Is it doable to process a Bill Only Sales Order for an ATO Model?

There was a Bill Only sales order that was processed that had an ATO Model in one of the lines. The other lines Closed and immediately got invoiced. However, the ATO Model is still in Awaiting Fulfillment and could not be progressed. We need to bill the customer. When we try to Progress the Order, it gives the message "APP-ONT-251015 There are no eligible activities to be completed. There is at least one defferred or externally notified activity in this flow. Please see the wotkfloe monitor or status window for more information"

Is there a way to progress this bill only order so that the ATO Model line will invoice?