Importing Payments, Z-Invoice is thinking of them as credits

Importing Payments, Z-Invoice is thinking of them as credits

I have recently added customers to the invoice section, then ran a separate import on invoices, which was successful. I have now attempted to import payments and instead of allocating it as a payment against the customer it has added it as a credit to be applied.

I get the below......

Credits available for this customer

A credit of $101.96 available for this customer. Click here to use these credits for this invoice.


Obviously I want the payment to record as a payment - am I doing it wrong? Any ideas?