Pay Twitch bits, couldn't be more complicated?

You want to support a streamer and the payment doesn't work out. Neither Giropay nor credit card, although both are displayed for selection. Account has sufficient funds, cards in order, entries correct and nothing works. If you go to their help pages, you won't get anywhere and you can forget about the support in English because you won't find a suitable field there. I can't speak English that well either. I don't feel like buying an additional payment service such as paypal or amazon pay. The question now is why the payment methods are offered when it doesn't work. Or how you can find out if my bank is refusing to pay because twitch doesn't suit you. I also find it uncomfortable to have given two sensitive pieces of data to twitch without success.

Maybe someone has experience with it and can explain it to me.

Sensible "actors" usually also offer via PayPal, I'm a member of a foreign software board and there the "admin" created the possibility to send a donation via PayPal after several people explained this "problem".