Resolving SIMATIC NCM PC Manager Download Failures Between PC

1. Problem Description

A configured SIMATIC PC Station pair—typically an Engineering Station (ES) and a Server/Client Automation Station (CAS) running WinCC, WinAC, or OPC—refuses to accept a project download initiated from SIMATIC NCM PC Manager. Both stations are configured, joined to the same SIMATIC HMI workgroup, visible in SIMATIC Shell, reachable via ping, and connected through a NAT-based virtual network. During the download the dialog raises a notification such as:

"Possible wrong target path or a problem with availability of the target station."

The notification is generic by design and is raised by the S7DOS / S7-SLS download path before the configuration data is committed to the target PC Station. This article walks through the diagnostic checklist that resolves the failure in almost every NAT/VM and bare-metal deployment: target share, Windows authentication, the role assigned to the remote PC Station, the SIMATIC Shell view, and the Symbol File Configurator that must be closed before each download.

2. SIMATIC PC Station Architecture

A SIMATIC PC Station is a Windows-based runtime container that hosts one or more SIMATIC NET components (S7-1613, OPC Scout, WinCC flexible Runtime, WinAC RTX, etc.). Each PC Station is configured in NCM PC Manager and is identified in the STEP 7 / SIMATIC NET project tree by its PC Station name, which must match the Windows computer name exactly (case-insensitive, but spaces are not permitted by S7DOS naming rules).

NCM PC Manager maintains a local configuration database (pcintern.cfg + indexed components) that mirrors what STEP 7 SIMATIC Manager pushed during the last "PC Station > Download" operation. If this database on the target machine is corrupt, out-of-sync, or has never been initialized, every subsequent download from the ES will fail with a path/availability error.

3. Root Cause Analysis

The NCM download error chain has six common failure points, in order of probability:

1. Target path not reachable as a UNC share. NCM does not write to C:\Programs\Siemens\Automation\... directly across the network. It writes to a UNC target path such as \\REMOTEPC\Siemens\Automation\... that is exposed by the SIMATIC NET "Project Share" service. If the share is missing or the directory inside the share is wrong, the availability error fires immediately.
2. Windows authentication mismatch. The Windows user on the ES that is performing the download must have write permission on the remote SIMATIC project share. Identical usernames with identical passwords on all VMs is a necessary but not always sufficient condition—local group policies (e.g., Access this computer from the network, Log on as a batch job) and UAC elevation can still block the write.
3. Remote PC Station is configured only as SERVER/CAS, not as ES. To act as a download target from another ES, the station must have the ES bit set in its NCM station configuration so S7DOS accepts an inbound download. Without ES capability, the download dialog reports availability failure.
4. Symbol File Configurator is open on the target. Per the official SIMATIC NET installation notes, the Symbol File Configurator must be closed during the download of the project engineering PC station; otherwise the file lock conflicts with the inbound write.
5. S7DOS service not running or wrong station index. The SIMATIC NET S7DOS service (or the older S7SVCxx in legacy SIMATIC NET) must be running on the target PC Station, and the configured station index must match the project.
6. NAT / firewall blocks Siemens ports. NAT must route ISO-on-TCP port 102, the S7DOS broadcast range, and the Microsoft SMB ports 445 + 139 between the two VMnets. NAT without inbound port mapping for these services will pass ping but fail all NCM operations.

4. Prerequisites

• STEP 7 V5.5 + SPx (or TIA Portal with SIMATIC NET PC software) on the ES.
• SIMATIC NET PC software installed on both target PC Stations with matching version (e.g., SIMATIC NET V8.2 or V14/V15/V16).
• Windows administrator account with identical username + password on both VMs (per Windows networking constraint for Kerberos/NTLM trust on NAT segments without domain).
• Network connectivity confirmed via ping <computername> AND net view \\<computername> from both directions.
• SIMATIC HMI workgroup identical on both stations (default SIMATIC HMI).
• Firewall rule allowing inbound TCP 102, TCP 445, TCP 139 on the target VM, and outbound on the ES.

5. Step-by-Step Resolution

5.1 Validate the Target UNC Path

1. On the ES, open a command prompt and execute:
   net view \\REMOTEPC
   If the share list does not contain Siemens (or the custom share name you configured in SIMATIC Shell > Settings > Project Share), the download cannot succeed.
2. Test write access with:
   echo test > \\REMOTEPC\Siemens\Automation\write_test.tmp
   A successful write proves the share exists and the user has write permission. Delete the file after the test.
3. In NCM PC Manager on the ES, right-click the target PC Station > Object Properties > Target Path. The path must be in UNC form, never a drive letter. Correct examples:
   \\REMOTEPC\Siemens\Automation\Projects\Plant01
\\10.0.2.20\Siemens\Automation

5.2 Correct the PC Station Role Configuration

If the target PC Station is only configured as SERVER or CAS, the ES cannot push a project download to it.

1. Open the SIMATIC project on the ES in SIMATIC Manager.
2. Select the target PC Station in the component view.
3. Right-click > Object Properties > Station tab.
4. Check the Engineering Station (ES) role checkbox in addition to SERVER or CAS as required.
5. Save and recompile (Station > Save and Compile).

5.3 Synchronize the SIMATIC Shell Project Share

1. On the target PC Station, open SIMATIC Shell (Start > Siemens Automation > SIMATIC Shell).
2. Right-click > Settings > Project Share.
3. Confirm the share name (default Siemens), path (default C:\Programs\Siemens\Automation), and Access setting (read/write for the engineering user).
4. Apply the share. SIMATIC Shell automatically creates the Windows share Siemens with appropriate ACLs for the local SIMATIC HMI group.

5.4 Confirm Symbol File Configurator is Closed

Per the official SIMATIC NET installation readme (SIMATIC NET – Support Readme), close the Symbol File Configurator on the target PC Station before initiating the project download. The file lock it holds on the configured symbol database (.sdf / .sbl) blocks the inbound write from NCM and produces the same generic path/availability error.

5.5 Re-Initialize S7DOS and the Configuration

1. On the target PC Station: sc query S7DOS — confirm state = RUNNING.
2. If the state is STOPPED, start it via sc start S7DOS or from Start > Siemens Automation > Station Configuration.
3. In NCM PC Manager on the target machine, perform Station > Import Station to re-sync the local config with the project from the ES before retrying the download.

6. Network and Share Configuration

In a NAT deployment between two VirtualBox/VMware VMs, configure the virtual switch for NAT Network (not plain NAT), so that both VMs share the same address space and SMB broadcasts function. Plain NAT (one-to-one address translation through the host's external interface) breaks the broadcast-based station discovery and often the SMB session as well.

7. Authentication Requirements

Identical local administrator credentials on both VMs are the minimum requirement when no Active Directory domain is present. Verify the following local policies on both machines via secpol.msc:

• User Rights Assignment > Access this computer from the network — must include Administrators (and SIMATIC HMI if that local group is used).
• User Rights Assignment > Log on as a batch job — required for the S7DOS service when it authenticates a remote user.
• Security Options > Network access: Sharing and security model for local accounts — set to Classic when using matching local accounts.

If UAC is enabled (default on Windows Server 2008 R2), map the network drive from an elevated command prompt so the token is fully privileged before NCM inherits it:

8. ES Station Configuration

A common error is to treat the ES role as optional. NCM PC Manager requires every PC Station that can receive a download to declare the ES capability, even if it is otherwise a SERVER or CAS. The configuration is stored in pcintern.cfg on each target and is propagated by the project download from the engineering source.

To add the ES role without re-creating the station:

1. In SIMATIC Manager, select the PC Station.
2. Right-click > Station > Open with NCM PC Manager.
3. In NCM, right-click the station name > Properties > Roles.
4. Tick Engineering Station (ES).
5. Save and exit; the change is committed during the next Download to Target Station from the ES.

9. Verification

After each fix, verify with the following sequence before declaring the issue resolved:

1. net use on the ES shows an active session to \\REMOTEPC\Siemens with no ERROR entries.
2. NCM PC Manager > Station > Download to Target Station completes without a path/availability prompt.
3. The target's Station Configuration Editor shows all configured modules (WinCC, S7-1613, OPC, etc.) in Running state.
4. Run Station > Diagnostics > Online from NCM on the ES; the target reports OK for each configured component.
5. In SIMATIC Shell on the target, the imported project from the ES appears under the project tree.

10. Troubleshooting Matrix

11. Backup of Downloaded Programs

Once the download succeeds, capture a backup immediately. In NCM PC Manager on the target, Station > Export Station writes a self-contained project snapshot to C:\Programs\Siemens\Automation\Backup\<timestamp> or any chosen UNC path. Schedule this with Windows Task Scheduler on each PC Station to retain a 30-day rolling archive aligned with the engineering change log.