Receipts in AR vs Payments in Advanced Collections

Hi,

A receipt is captured against a customers account in the Receipts Workbench in Oracle Receivables for a payment that the customer has made into our bank account. If a promise to pay was captured in Collections, I can see the PTP and I can see the Receipt as captured in AR, but the invoice remains delinquent?

Why is this and how can this be rectified?

Must the payment that the customer made be captured via Collecitons?

Any insight would be appreciated.

Thanks