Hi everyone,

I'm working with TIA Portal V20 and S7-PLCSIM V20. My setup includes an ET 200SP, CPU 1512SP F-1 PN, and my HMI is a TP1200 Comfort Panel, connected to port X2.

The issue I’m facing:

• When I simulate only the PLC, everything works fine, and I can go online.
• However, when I start the HMI simulation, it fails to connect to the simulated PLC.
• I get the following error:
  "Connection disconnected: HMI<>PLC, Station 10.10.10.10, Rack 0, Slot 1."

What I have checked so far:
✔ The IP address settings are correct (10.10.10.10).
✔ The HMI connection settings in TIA Portal are configured properly.
✔ PLCSIM is running and online before starting the HMI simulation.
✔ I tried different startup orders (PLC first, HMI first, etc.), but no success.

Note: Two weeks ago, when the setup was here, i simulated the HMI on the PLC, and everything worked fine.

Has anyone encountered this issue before? Any suggestions on what might be causing this?

Thanks in advance!

The X1 port of the PLC has the IP address 192.168.0.10, and the X2 port has the IP address 10.10.10.10 (as seen in my screenshot in the original post). The HMI has the IP address 10.10.10.30. I am able to download to my simulated PLC via port X2.