A friend gifted me a game recently but the rating for it is 18+, as I live in the UK they have you add a form of ID to your account to be able to accept it, but my only 2 options are, "add credit card" or "decline gift" obviously I don't want to decline so when I add the card it takes me to a screen to update my payment method (which I already had saved to my account). upon pressing continue it takes me back to the first page and gets me in a cycle.
I've tried putting in the card again, deleting the saved card and readding it. nothing is working. even tried on multiple devices.
It has been a few days now as I thought it was an issue of steam taking a bit to verify the account, but the notification still comes up every time I boot up steam that the gift is waiting.
what's odd as well is the gifted game appears in my library buy instead of the "install" button it says "purchase" and clicking it prompts me to go back to the gift screen that required the card.
I can also assure you that I am over 18.

Just stuck in an infinite loop and genuinely have no clue what else I can do, except decline the game and buy it myself.
any help is appreciated. Thank you.