This issue seems to happen from time to time for some users for some reason that has never been explained by 48.
You'll have to contact 48 support in order to get them to look into and fix this for you.
You'll have to persist if they say that they can't help.
What exactly did they say?
I'm assuming that the issue isn't with your card - e.g. it's still valid and hasn't expired, you have enough cash in your account if it's a debit card, the card isn't frozen via your online banking, etc.?
To contact 48 support see the links in my signature below.
You might want to try calling the number provided.
