Invoice numbers not generating for partner

For some reason, when my partner completes a file, he is not generating an invoice number and PAID isn’t showing up after payment is registered on the billing page/client invoice. His settings are exactly the same as mine, so I can’t see a reason for this. He does work off site sometimes, but don’t see why that should matter.

We are a small business, so it isn’t a huge deal to manually enter them, but I know we shouldn’t have to. Any idea why this might be happening. I found another thread, but the solution didn’t apply to my problem.