I can't assign a new technician to new appointments on the existing jobs, as I am getting Action is cancelled, at least one managed technician must be assigned to this appointment, since the job total >$0 error message.
Solution
Set technician splits
This error message occurs when the technician assigned to the job is unmanaged or deactivated. To resolve the issue:
Open the invoice for the job.
In the side menu, click Adjust Splits.
Change the splits so that the managed and active technicians have 100% of the splits, and the non-managed or deactivated technician has 0%.
Split determines how much credit each technician is getting for the job. For example: If two technicians perform work on a job, the split could be an even 50%-50%, or it could be 75%-25% if the first technician did a bulk of the work.
By default 100% of the technician split will go to the first technician assigned to the job.