Hi, probably the best solution. On my side I did not went until here.
I deleted the folder /Users/Shared/GOG.com/Galaxy and reinstalled Gog.
After that it was working again.

I assume the solution from reddit is better because it does not require a complete reinstall of Gog.

Doesn't works on my system (Mac m2). And why does this software need to "talk" to background services that start at launch?! There is absolutely NO REASON for just downloading apps.

Thank you for sharing. This helped me! I went and deleted the Galaxy Folder. And reinstalled GOG. It seems to be working after that! It was weird, cuz I could see the program loading in the background and then suddenly the message box would pop up! I am glad its over now!

DraganGaic post work for me too, thanks.

I'm having the same problem, and I've tried the solutions mentioned and referenced here. I've used the terminal to launch the GalaxyCommunication service. I've made sure that the two startup items were enabled in Settings>Login Items. I've made sure that the Galaxy client is listed as being allowed to receive incoming connections in Mac Firewall. I've turned Mac Firewall off. I've uninstalled Galaxy, removed its folder from User/Shared, and reinstalled. That last time, it was about to start up, the interface loaded, then it threw the error and died. When I first installed the Galaxy client last week, I initially had problems with its interface going blank if left idle for a while. I think i reinstalled. Then it worked fine since then, until today, when the error keeps popping up and crashing Galaxy. I'm on an M1 Mac Mini running macOS 13.5.1 Ventura.

Update to my situation: I changed the size of the macOS' Menu Bar under Settings>Accesibility>Display. That change requires logging out and logging back in, which I did. Galaxy launched and successfully started with no problem.

I have no idea how it fixed itself.

Worked for me too (when the other solutions didn't).

I'm guessing because changing the macOS menu bar size requires you to log out. You could probably get the same effect by simply logging out and in again.