Something changed in the styling of the payments.wikimedia.org forms. On desktop they now have a blue border and white background which was hidden before. Worse they are pushed off to the side and not fully visible on mobile.
I think this is due to https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/DonationInterface/+/517583/ interacting badly with some on-wiki styles. The quickest fix would be to revert that change, and then I can take a closer look at cleaning up the styles if needed