Funny thing is that I use Scaleway also, and did not have any problems registering a credit card with them. Since online.net and scaleway seem to be the same or related somehow, maybe they should copy-paste the CC validation code from them or allow login with the same user.
Same for me. I wanted to use them two weeks ago but could not get passed it. I just gave up on 3rd card attempt. And btw why can't they support pay-pall? It always makes me uneasy to pass in the credit card details directly on a site.
Seems that under the guise of security it seems that sites can leave their payment process to be complete crap (UX/UI, feedback and everything else). I see this far too often; sometimes not even the "Error" appears, just a page reload without any indication. It is not that hard to be clear guys...