Occasionally, patching issues can occur when certain game files become corrupt. Using the "Verify / repair" function in GOG Galaxy will fix any corrupted files.
How to repair files:
- Run GOG Galaxy.
- Click Gwent on the installed games' list on the left side.
- Press MORE button, select "Manage Installation" and then "Verify / repair".
- Wait. The repair function can take time depending on the number of corrupt files it has to repair.