Problem
The problem is that when you add an item in the estimate which acts as a discount, you get the Non-zero estimate item that can't be added to the estimate from a job with unmanaged technicians error.
Solution
This issue occurs because you update the sold by information in the Estimate screen > Update Estimate before adding tasks.
To solve the issue:
Make sure that the job's splits are assigned to a managed technician
Update the technician who sold the estimate in the opportunity Follow Up screen
Add tasks before updating the estimate details
Make sure the job's splits are assigned to a managed technician
Open the job's invoice and click Adjust Splits.
Make sure that 100% of the job's splits are assigned to managed technicians.
Update the technician who sold the estimate in the opportunity Follow Up screen
To update the technician who sold the estimate:
Go to the navigation bar and click Search.
From the dropdown, select Estimate.

Select the estimate which you want to update.

Click View Opportunity.

The Opportunity Follow-Up screen opens.
Click Sold/Convert.
From the dropdown, select the technician.
Note: Make sure to select a managed technician who has splits on the job. For more information, see Managed technicians and non-managed technicians.

Add tasks before updating the estimate details
To add tasks:
Go to the navigation bar and click Search.
From the dropdown, select Estimate.
Select the estimate for which you want to add a task.
The Estimate screen opens.Click Add a task.
Note: For more information, see Add an estimate to an existing job and create a project.

It is recommended to add tasks, then update the estimates to avoid getting the Non-zero estimate item that can't be added to the estimate from the job with unmanaged technicians error.
Note: If you have already added a sold by on the Opportunity page, this field is populated by the user who was assigned as a sold by.
