Once Flowrev generates a recognition schedule for an invoice or bill line, that line's recognition parameters including the service dates are locked.  

Sometimes users need to create a different schedule.  To do this they have to first cancel the existing schedule, which unlocks the invoice line and allows the creation of a new schedule based upon new recognition parameters set. 

This can be done from the invoice detail page within the schedule panel below the invoice line listings. For details see this article:

What happens when I cancel/reverse an invoice line schedule?

NOTE: If you make changes to invoice or bill lines in your accounting system after you have created a schedule in Flowrev for the line, the line will not be updated and you will receive a message noting this when you run "Update Selected".  To update such lines, user have to delete the schedule prior to pulling over changes from their accounting system.