It would help us to debug the issue if you could open an issue at http://mantis.gog.com and submit your logs (instructions are provided on the ticket submission page).

Both your accounts (HeyItsRed and Its_Red) are authorised to play Gwent.

It looks like you're using two different accounts, and one of your accounts does not own the "4k graphics assets pack" which causes the issue you've described. You can either add the 4k pack to both accounts, or uninstall the pack from the Windows Control Panel. The 4k assets pack does not improve the graphics in any way on non-4k screens, and is separated from the base game, so that players don't have to download huge unused files.