we're still using the SCOM 2019 evaluation edition, management server, sql server are on the same VM. it's been working okay up until two days ago, the newly agents we pushed out to our systems would show up as "not monitored". I've tried the following steps but still having the same issue:
I've stopped the Health service, rename the Health service folder and restarted the Health service
place that particular agent in maintenance for 10 mins and then took it out of maint.
doubled checked the firewall settings made sure all ports are opened
it was around the same time i start noticing "All Management Servers Pool Unavailable" error. The time of that error coincides of me restarting the Health service couple days ago to test a batch program (which is completely unrelated to the "not monitored" issue.