Tests stop after 20 executions and agent needs reregistered

I have scheduled job with one test, runs every hour. It runs fine for a few hours, even upto 20 but then suddenly stops working and I have to re-register the agent otherwise it will just not execute and when tests I manually trigger don’t even go into executions until I re-register the agent.

I’m lost as to what is going on, and its tiresome having to re-register the agent every day, if anyone has any insights it would be greatly appreciated!