Hey, @TSkaff initially reported this and I experienced it as well on my end. Very possible that it's anti-fraud related.
We were both able to donate via the variant; in my case, I made four one-time donations, adding an upsell twice, before I started to consistently see error messages like the one I've attached.
Expected behavior: after selecting an amount and entering the contact info, clicking a particular credit card type will open the iframe.
Observed behavior: Gray Continue button loads where iframe would normally appear (screenshot Error01a), and error message appears at top of form (screenshot Error01).
These error messages persisted across my phone and desktop, and also while attempting to give via my spouse's credit card (screenshot Error02).