Hi Mihai,
Thank you for your suggestion. Today, I installed a different theme (and even without deactivating the plugins), the credit card form from EDD-Stripe worked well.
In fact, the issue is with my theme.
Do you know if there is a easy way to…
(a) bypass this problem with my theme (e.g. by adding a function to my theme)? It is an old theme.
Or
(b) to redirect the buyer to an “external checkout page” only when the credit card option is selected? I know Stripe has prebuilt checkout pages
PS: I said “easy way” because I don’t know PHP language, but sometimes I edit small pieces of code.