We all know how to process payments. This is not the issue. If you read through the post you'd see that the issue is the customer gets an error saying they have to try again later to pay the invoice. The problem is that the customer record has become corrupt and either:

1 - Change the name slightly in the current customer record by inserting a dot "." in the name OR

2 - Inactivate the current corrupt record and create a whole new customer with a slightly different name such as putting a dot "." to make QBO think it is a new record.

3 - Then send out the invoice for payment.

I hope this will help everyone!