Posted December 03, 2021

When I've had similar problems in the past (card rejected without the bank seeing any authorisation attempt) it has always been due to GOG's payment processor being over-zealous with their blocking. Aside from waiting for support to get back to you, the next best thing may be to try a cash-card like the PaySafeCard, if that option is available to you on checkout - the checks on that may be less draconian.
Also, check that any web-filtering plugins that you are using (e.g. uBlock, Privacy Badger, uMatrix) are either configured to allow the card-processor domains - or are temporarily disabled when trying payment.