Summary
When you create a series with a Billing Frequency other than For Every Work Order, and then change the frequency to For Every Work Order after the first Work Order is complete, an invoice is not automatically created when the next Work Order status is set to Complete.
Key Points
The system cannot retro-actively create an invoice for a completed Work Order, it can only do it for future Work Orders
The next invoice will be sent based on the original Billing Frequency
Follow one of the two work arounds
To see when the next invoice date is, edit the Work Order Series and change the Billing Frequency to the original frequency and the Next Invoice Date will appear.
To work around this, either:
Change the Next Invoice Date to tomorrow's date
-or-
Cancel the series, and create a new series with the Billing Frequency set to For Every Work Order