With a Debit (Bank) Card, I'm not sure if the Registration and email would be sent immediately, but when the transaction and funds are transferred.
It could be that since this transaction was only yesterday, a weekend. I would give it a few days to see if it resolves itself.
If not you can contact avast using a support ticket, but that would require some information, email (from avast) and order ID number so that they can find your order.