@davidadams , Welcome to the Community!
Since your products were modified in November, the system has suppressed the invoice for this month.
There are now two options for you:
1. you pay the usual amount with an old payment slip, which you have paid every month. This amount will then be deducted from the December invoice.
2. you wait for the December bill, which then consists of two monthly periods.
Greetings
Daniele