Primary ZCM Server - Corrupted SSL Certificate

Hi All -

Our primary ZCM server has decided it no longer likes the SSL certificate that has been working on it perfectly for over a year.

First some background - we're using an External CA - a Microsoft AD CA server. I have no idea what would have prompted this to break - it was working perfectly until about 3 days ago and it just randomly broke.

I'm thinking maybe the server lost it's registration as the primary server or something? I can't do a zac reg on it - it gives the following error:
"Unable to register with the server at: https://
RegistrationManager - Network error connecting to server: The underlying connection was closed: Could not etsablish trust relationship for the SSL/TLS secure channel"

I tried going through the procedure to add an external CA again, and it successfully went through that. I'm unable to succesfully do the zac register command, however.

Are there any logs that can be looked at for this? Maybe the entire SSL setup needs to be deleted and recreated? Any help would be greatly appreciated as our server is currently not able to service any requests.

Thank you.