Apply a balance to unpaid invoices

I have a client that tends to pay through their online portal, and often their payment isn’t applied to an invoice. I’m guessing they are just clicking something wrong. Typically I would just go in and apply their balance towards the invoice.

Today I went to do so and don’t see the little link for “Apply balance”. Has it been moved? How can I apply their balance to outstanding invoices?

Whoops, I didn’t notice that this client was paying an overdue invoice… my fault, confusion all around. Issue solved!