I have an Open Invoice and an Open Credit Adjustment or Payment. However, I can not pay the Invoice neither with the Credit Adjustment nor with the Payment.
There is no "Apply Payments" button on the Invoice screen and there is no "Adjust Document" button on the Credit Adjustment or Payment screens.
The Invoice in question balance is greater than the Payment or Credit Adjustment balance.
Invoices can not be paid partially. There are no other Payments or Credit Adjustments for the customer in question, that is why the "Apply Payments" button is missing under Top > Billing Director > Receivable > Documents > Invoices > Invoice in question.
There are no invoices whose balance is lower or equal than the Credit Adjustment or Payment balance, that is why the "Adjust Document" button is missing under Top > Billing Director > Receivable > Documents > Payments > Payment in question or Top > Billing Director > Receivable > Documents > Adjustment > Credit Adjustment in question.
To pay the Invoice with a Payment or Credit Adjustment, please create a new one with its balance greater or equal than that of the Invoice.