Microsoft has released security updates for vulnerabilities found in:
Exchange Server 2013
Exchange Server 2016
Exchange Server 2019
These updates are available for the following specific...
Updated May 04, 2021
Version 8.0
Blog Post
Sorry for the repeat post, I was on Exchange 15.1.2176.2 (CU19) which then broke. I downloaded Exchange CU20 and installed. This still did not resolve. Digging through the event log, I found repeatedly
event ID 15021 HttpEvent, An error occurred while using SSL configuration for endpoint 0.0.0.0:444. The error status code is contained within the returned data.
Doing some digging I found this article. https://www.vcloudnine.de/microsoft-exchange-2013-shows-blank-ecp-owa-after-changes-to-ssl-certificates/
I followed those instructions and got my server back! PowerShell, OWA and ECP and mailflow are working now. I had never changed SSL certificates in the last year and I know OWA, ECP, PowerShell and mailflow all were working before I did this update.
I think I should hold off on this update till we get some more information on what is going on.