You'll need to provide a bit more information and context than that if you want assistance from the Community Forum.
What exactly do you mean by "credit"?
Cash credit?
Membership plan?
Add-ons?
What happens when you try to buy it?
Any error messages?
When were you last able to successfully buy stuff on 48?
Is your payment card still valid, not frozen via your online banking, and they're are sufficient funds in the account if it's a debit card?
If you need to contact 48 support about this then see the links in my signature below.
