Issues with WMI and DCOM

Hi,

For a while now, I've been having issues with WMI and DCOM rendering OpManager only half as good as it was before. From my OpManager server, I am unable to authenticate to any other server on my network so none of my stats including memory and CPU usage, SQL information, etc. are showing up on any of the systems in OpManager. I've had several support requests but have yet to find a solution so I'm reaching out to everyone to see if anyone else has any ideas. The specific error I receive is "A security specific error has occurred" and this shows when trying to use WMI through OpManager. Here are the steps I've taken to try and resolve this:

Disabling the firewall completely
Checking DNS for errors
Tried different accounts including other Domain Admins
Tested on unpatched computers with no AV and no Firewall
Checked for GPOs that can block these services
Assured DCOM, WMI and RPC are running

I'm sure I've tried other stuff too but I'm at a loss at this point and if we can't get this fixed by renewal time, we won't be renewing. If anyone has thoughts, please let me know.

Thanks so much.