I cannot pay through websites

Contact your payment provider first, and then contact Instagram Support.

You want to give both of those entities money, so they both have some motivation to get this fixed.

Whether this is a bug or a rejection at the payment provider, or something (not) happening at Instagram or the Instagram payment gateway, or is something with Apple Pay, your financial provider and Instagram Support are in the best position to troubleshoot.

(Nobody around here in the Apple forums can particularly help with this past suggestions, and nobody here can see into the related transaction logs.)

We are fellow users and can’t help directly w/ your accounts.

However we CAN help.

What payment method are you attempting to use within ApplePay?

(e.g. AppleCash, Credit Card, Debit Card, … )

Also MANY websites still do not yet accept payments via ApplePay.