maybe try at an atm first, see if that works?
I'll try that too tomorrow, thanks.
What type of transaction was it? Anything prepaid won't work when you're buying fuel in my experience, I really don't know why, and that goes for non crypto prepaid cards in every country I've tried it.
Elsewhere they may pre authorise even on an in person transaction and if you don't have more than what you're spending on the account it may not cover it.
I've had more than a few sites reject my old Xapo card. When I called up they couldn't tell what type of card it was.
It was at a grocery store, which used to accept Wirex cards in December.
I'll give it another try tomorrow in a store and maybe also see at ATM.
Thanks for the answers, it seems that at least I didn't forget any step. If tomorrow still doesn't work, I'll go for their support ...
PS. Last year I've bought fuel with Wirex... just I paid "inside", not directly "at the pump".
Edit 2018-05-04: Today it worked in another store. Maybe because it's banking day, maybe because this time I used the card normally, not contactless. I didn't have to go to ATM.