Please shut down Galaxy by right-clicking its icon in the System Tray, and selecting Exit. Afterwards, re-open Galaxy, click Gwent in Galaxy’s side-bar on the left and try launching the game again.
It may also help if you go to playgwent.com and log in there with your account. Make sure to restart Galaxy afterwards.
If the problem still persists after following the steps above, try whitelisting these two GOG Galaxy folders in your anti-virus/firewall software:
- the GOG Galaxy installation folder (by default C:\Program Files (x86)\GalaxyClient),
If the problem persists after trying the above, please contact us.