If you've been assigned an apprentice that no longer reports to you, you can reassign the apprentice to the appropriate supervisor. Find the apprentice in your Apprentices section and go to their page. From there, click on Supervisor and you should see their supervisors listed.
Click the orange + icon to edit the Primary Supervisor. If the supervisor you're looking for is in the list already, simply click Make Primary. If not, click the + to Add supervisor at the bottom. Type the supervisor's name. If they're already in the system, you can click on them to add them.
If not, click on the plus next to their name to invite them by email. Once invited, you should select Make primary, to ensure the new supervisor receives notifications about the apprentices' hours.