Problem
Users can't edit the Main Zone due to a lack of permissions. The error message says, "You do not have permission to edit this field."
Solution
Enable user permission
In Enterprise Hub, go to User Management.
In the side menu, click Roles.
Find and select the corresponding user's role who cannot make the change.
Click the role.
Click the ServiceTitan permissions tab.
Under the Dispatching sub-section of the Job Booking & Dispatching section, enable the Edit zone permission.

When finished, click Save Changes.