If you attempted to make a payment in-game with real life currency and it didn't get through, make sure that you're launching GWENT through GOG Galaxy and have Galaxy Overlay enabled. To do so:
- Go to Settings in GOG Galaxy -> Game features -> In-game features -> Enable Overlay.
- In order to enable Overlay for GWENT, right click on GWENT in the GOG library -> Manage installation -> Configure... -> Access GOG Galaxy features in-game.
Additionally, some applications that have their own Overlay feature may interfere with Galaxy Overlay, please make sure that you're not running such programs in the background.
If the above solution doesn't help, please refer to the steps available in this article