Can you check whether OMSA services are running. You can refer below link for more details

https://www.dell.com/support/kbdoc/en-in/000134420/troubleshooting-for-openmanage-server-administrator-if-not-opening-updating-or-showing-correct-information 

If above is not solving the issue can you reboot the server and check. You can also uninstall and install OMSA and check. Can you also check whether iDRAC is functional on this server?

I've already tried restarting and reinstalling the service, but it didn't work. Server reboot is not possible due to circumstances. What should I check in IDRAC?

Can you run "racadm getsysinfo" command from the host OS and check whether it is giving proper output

The following error occurs when running racadm getsysinfo. What is the problem?

Looks like iDRAC have some issues. Can you reboot iDRAC by pressing identify button on front of the server for 15 seconds and check the behavior. You can refer below link for details

https://www.dell.com/support/kbdoc/en-us/000126703/how-to-reset-the-internal-dell-remote-access-controller-idrac-on-a-poweredge-server#:~:text=In%20order%20to%20reset%20the,without%20changing%20any%20saved%20settings. 

Hi, Can you check if the iDRAC is reachable or not? I saw this error while iDRAC is not reachable. Please do iDRAC reset from here https://dell.to/3LEaHVn

Then please check iDRAC and BIOS is up to date if not please try to update here https://dell.to/3LR3Fgl

Also you can try to use iDRAC tools for same racadm cmd https://dell.to/3LJn6aD