Siemens NetPro Cannot Display Connection: Resolving STEP 7 UI Error

When opening SIMATIC NetPro in STEP 7 (SIMATIC Manager), engineers occasionally encounter a "Cannot display connection" / "Keine Verbindung anzeigbar" state in which the connection table appears blank, partially hidden, or completely inaccessible. The PLC program, hardware configuration, and project integrity are typically unaffected; the fault is a corrupted or dragged NetPro window layout inside the STEP 7 IDE. This article documents the root cause, the canonical fix, the verification steps, and adjacent errors so the engineer can resolve the issue without rebuilding the project.

1. Problem Description

Symptoms reported by the field engineer when opening NetPro on an existing STEP 7 project:

• The NetPro window opens to the project but the connection table area is empty or invisible.
• A grey horizontal splitter bar sits at the very top of the NetPro window directly below the toolbar.
• The text "To display the connection table, drag the splitter bar to the middle of the window" is visible but the table itself is collapsed to zero height.
• No selection, no scrollbar, no headers (Local ID, Partner, Partner ID, Type, Active/Passive) are present.
• The error message returned when querying a connection is "Cannot display connection" or "Es kann keine Verbindung angezeigt werden".
• Other STEP 7 projects on the same PC open correctly in NetPro, ruling out an installation defect.

See the official Siemens NetPro help for context on the connection table layout: Siemens Entry ID 14044958 - NetPro Online Help.

2. Root Cause Analysis

NetPro is implemented as a multi-pane MDI window inside SIMATIC Manager. The connection table sits in the lower pane of a vertically split view. A draggable horizontal splitter bar separates the upper pane (graphic of the S7 station with the CP module(s)) from the lower pane (the connection table grid).

Two distinct root causes produce the same observable symptom:

The error string "Cannot display connection" is a generic message returned by the NetPro OCX control when the lower pane container has no visible client area in which to render the connection list. The connections themselves are present in the offline SDB container (System Data Blocks, type SDB 0/1xx) within the project, but the UI cannot enumerate them.

2.1 Why the splitter bar position is sticky

NetPro persists the splitter position, window size, and window coordinates in the Windows registry under:

HKEY_CURRENT_USER\Software\Siemens\Automation\NetPro\Settings
HKEY_CURRENT_USER\Software\Siemens\Automation\S7W\...\Layout

Until the splitter is moved or the arrangement is restored, the value remains corrupted and the UI reopens in the broken state regardless of which project is loaded.

3. Quick Solution (90 seconds)

1. Open the affected project in SIMATIC Manager and double-click NetPro in the project tree (or right-click the project → Open Object → NetPro).
2. Look at the very top of the NetPro window, immediately below the icon toolbar.
3. Hover the mouse over the thin grey horizontal bar. The cursor will change to a vertical resize glyph (↕).
4. Click and drag the bar downward to approximately the vertical midpoint of the NetPro window. The connection table populates immediately with all configured S7, ISO-on-TCP, TCP, UDP, FDL, and named connections.
5. If the bar is not visible (e.g. monitor disconnected), use the menu path Window → Restore arrangement. This resets splitter position, dock layout, and window size to defaults.

4. NetPro Architecture and Connection Types

NetPro is the offline/online editor for S7 communication connections. It is the only STEP 7 tool that can configure integrated and non-integrated connections, and it is mandatory for any project that uses a CP (communications processor) module such as CP 343-1, CP 443-1, CP 343-1 Lean, or CP 1613.

Once a connection is created in NetPro and the project is compiled and downloaded, the offline SDBs are written to the CPU and to the CP. The CP loads them at startup and uses them to authenticate incoming requests. If NetPro cannot display the table, no new connection can be added, so resolving the UI fault is a prerequisite to further configuration work.

5. Hardware Configuration Prerequisites

Before the NetPro connection list can be populated, the hardware configuration (HW Config) must contain the CP module(s) that will terminate the connections. Common omissions that cause confusion include:

• SM (Signal Module) inserted in the wrong slot, displacing the CP.
• CP added to the station but the rack is not saved (HW Config → Station → Save and Compile).
• Wrong CP order number (e.g. 6GK7 343-1EX30 vs 6GK7 343-1EX11) - the firmware version affects the available connection types.
• CP firmware version not matching the GSD/ICP file version installed in STEP 7.

To confirm HW Config is consistent:

1. Open HW Config from the SIMATIC Manager project tree (S7 station → Hardware).
2. Verify the CP appears in the correct slot (typically slot 4 in an S7-300, slot 4-15 in an S7-400 UR1/UR2).
3. Double-click the CP, confirm the IP address and subnet are configured under Properties → Interface.
4. Select Station → Consistency Check. STEP 7 reports any timing, addressing, or module-rule violation.
5. Select Station → Save and Compile. The SDBs are generated.

Reference: Siemens Entry ID 15364447 - Configuring S7 connections in NetPro.

6. CP Device Properties Affecting NetPro Display

Several CP properties, if mis-set, will prevent a connection from being selectable in the connection table even after the splitter bar is restored:

7. Restoring the NetPro Window Layout (Detailed)

If the menu bar and the splitter bar are both hidden, use one of the following recovery paths.

7.1 Menu path

1. Click anywhere inside the NetPro window to ensure it has focus.
2. Press Alt+W to open the Window menu.
3. Press R to invoke Restore arrangement.

7.2 Registry reset

1. Close STEP 7 completely (including the SIMATIC Manager background process S7Wsvap.exe).
2. Open regedit as the logged-in user.
3. Navigate to HKEY_CURRENT_USER\Software\Siemens\Automation.
4. Rename or export and delete the NetPro sub-key (and S7W layout sub-keys if the SIMATIC Manager is also broken).
5. Restart STEP 7. The application recreates the keys with factory defaults.

7.3 Profile reset

STEP 7 stores additional UI state in %APPDATA%\Siemens\Automation\<S7-Version>\Layouts and %LOCALAPPDATA%. Closing STEP 7 and renaming the Layouts folder forces regeneration on the next start.

8. Related NetPro Errors and Their Meanings

The "Cannot display connection" text is one of several NetPro messages that look identical but indicate different faults.

9. Verification After Repair

1. The connection table is fully visible with column headers: Local ID, Partner, Partner ID, Type, Active/Passive, Status.
2. Right-click the table → Connection → New... opens the New Connection wizard without an error.
3. Select PLC → Compile and Download Objects (or Save and Compile alone) and confirm no SDB warnings appear in the output window.
4. Open PLC → Online → Download to Target Station with the project connected to the CPU. STEP 7 reports each SDB loaded.
5. Right-click a configured connection → Connection Status. With the partner reachable, the Status column should read Established and the diagnostic buffer of the local CPU should contain entry SDB <n> loaded successfully.

10. Commissioning Checklist for a NetPro-Served Project

1. SIMATIC Manager: confirm STEP 7 version (V5.4, V5.5, V5.6) matches the project version. Mismatch causes display errors that mimic the splitter symptom.
2. Project → Check Consistency. Fix any red items before opening NetPro.
3. HW Config: rack full and saved; CP order number correct; IP/subnet assigned; connection resources sized.
4. NetPro: confirm splitter visible (this article's primary fix), all required connections present, partner type correct (S7-300, S7-400, PC station, unspecified).
5. Save and compile. Inspect SDB generation log.
6. Download SDBs to the CPU. Download SDBs to the CP (if the CP has its own memory card, transfer via PLC → Ethernet → Edit Ethernet Node or Assign IP Address via PRIMERON).
7. Online test: PLC → Diagnose/Report → Connection Status. All active connections should report Established.
8. Capture the NetPro window state to a PDF or printout for documentation. Print a Connection List report (File → Print Preview) - this is the legal record for the FAT/SAT.

11. Field-Proven Notes and Caveats

• If the project was last edited in TIA Portal and later re-opened in STEP 7, the NetPro display may appear blank. STEP 7 cannot open TIA-generated connection data without conversion. Either re-create the connections in STEP 7 or migrate the project to TIA Portal fully.
• Dual-monitor setups with different DPI scaling commonly produce the corrupted-splitter symptom. Set the same scaling on both monitors before opening NetPro.
• Touch-screen laptops frequently trigger accidental splitter drags because the bezel gestures are interpreted as left-mouse drag. Disable touch input when configuring connections, or use the keyboard navigation (Alt accelerators).
• The connection list reorders when the user changes the View → Sort. The "Cannot display" error never arises from sorting, but a sort combined with a collapsed splitter looks identical to a real fault.
• STEP 7 V5.4 against Windows 10 1903+ has documented issues with MDI splitter persistence. Siemens published hotfix STEP 7 V5.6 SP2 HF5 addressing splitter handling. Apply the latest Service Pack before troubleshooting further.
• NetPro is read-only when the project is opened with Open as read-only. The connection table renders but new connections cannot be added. This is a common source of "I can see the table but cannot click anything" reports.

12. Frequently Asked Questions