First of all, SYSTEM cannot be the user when InteractiveToken is used since SYSTEM cannot run interactively. Please check the documentation on this site to see how to correctly call RegisterTaskDefinition using the SYSTEM account.
If, after making that change, you still experience the error, please let me know which OS versions are running and the status of the account connecting to the TaskService (admin, user, etc.).
If, after making that change, you still experience the error, please let me know which OS versions are running and the status of the account connecting to the TaskService (admin, user, etc.).