The Job Type Default issue is introduced with Dynamics 365 for Finance and Operations update to 10.0.28 version with setting activity number on closed project activities on job type setup forecast form.
This is the known issue in core Asset Management for Dynamics 365 for Finance and Operations where the underlying activity record is closed when a job type default record is created and therefore blocks the creation of a forecast (hours and items) against the job type default record.
To resolve the issue you need to...
- Create a ticket with Microsoft with a request to disable Microsoft "ProjActivityNumberCompletionCheckEnabledFlight" flight feature preventing forecast creation on closed project activities.