As @linkp noted the error you describe is because of extremely high number of failed requests.
I am puzzled because the domain you mention admin.mountainhighseo.comwas successfully validated for a cert issued Mar17 2025: crt.sh | 17193213650
I thought that should ensure that particular domain name wasn't considered a "zombie"
I am also puzzled as you said you got that cert 3 months ago. You got one on Mar17 and before that on Jan16 (and two more earlier than those for a total of 4 certs perfectly normal 60 day renewal schedule).
Is there a different cert request for just admin domain happening on a different system that keeps failing perhaps?
We haven't seen any problems with this yet so not quite sure how to proceed. But, yes, go ahead and post the full URL although put a space somewhere in the middle to avoid auto-clicks