Updated to the latest version, and now, about 30 seconds after logging in, every single time, I get the following message, whereafter Galaxy shuts down:

Connection to Communication Service was lost and could not be restored! GOG Galaxy will now shutdown.

So my client is effectively unusable. I can accept that there might be server issues, or connection issues in the client, but forcibly shutting down the client when it happens? That is entirely unacceptable. More so for a platform that prides itself on its DRM-freeness.

I have the same issue.

Got the same issue too and i looked in the logs for Client Communications and got this:

[GogPbConnectionManager] Failed to start listening; listenAddress=127.0.0.1:9977: error=Std Error: bind: Trying to access a socket in an unauthorised way.
[GalaxyCommunicationService] Caught runtime exception: RuntimeError: Failed to start listening on address 127.0.0.1:9977

This could mean the communication service was not launched with administrator rights ?

I also have the same problem.
I've reinstalled GOG (without any game and it worked) however after installing some games it re-appeared.
Tried everything mentioned on the gog forums - nothing worked.