Hi,

First of all, I would check the compatibility of the RT software version installed on the client PC (Operating System) ->Welcome to the compatibility tool

Further:

-What are the requirements for operating SIMATIC WinCC in a Windows network?

-Configuration of a Client–Server System with WinCC V7.5

-How do you remotely access WinCC stations (WinCC V7 / Professional / Unified)?

It is important to check that you are not accessing the WinCC server through RDP, since as indicated in the link above, it takes down the WinCC services.

Is the same WinCC version (exactly, with ServicePack and Updates) installed on both computers (server and client)?

How has the server project been started from the client? Have you used SIMATIC Shell?

I hope this helps to find the source of the problem!