Warsteyn: Seems to be an issue with cached data, have you guys read the post from Ilona ?
I'm unable to post a link here, else I would quote it because it's not my work and the KUDOS are hers.
Here's what she wrote - you can literally copy the paths into Windows Explorer because she uses %variables% , select the "steam" named file and SHIFT-DEL, then launch Galaxy again and re-connect Steam :
I've had a similar issue. My Steam integration was offline and unable to connect.
I found out that, for some reason, the plugin was unable to update to the new version.
So I completely closed Galaxy and deleted
steam_[..a bunch of numbers..]-storage.db file from %programdata%\GOG.com\Galaxy\storage\plugins\
and
steam_[..a bunch of numbers..] folder from %localappdata%\GOG.com\Galaxy\plugins\installed\
After the next Galaxy launch, I was able to download the new Steam plugin in the integration settings.
Connected again, and everything is working fine so far.