Note: this post is getting frequent updates; please keep checking back. Last update: 3/19/2021
Microsoft has released a set of out of band security updates for vulnerabilities for the following ver...
Updated Mar 19, 2021
Version 44.0
Blog Post
@ All who faced OWA/ECP broke issue post the installation.
I had the same issue on one of the nodes in the DAG. The installation did not say if it failed, however I could find an error in the event says the OWA could not load because the default theme file is missing in the directory "C:\Program Files\Microsoft\Exchange Server\V15\ClientAccess\Owa\prem\15.1.2106.13"
The target directory did not contain any files except a directory and hence I decided to re-run the patch as it seems the copy process did not go through well. A re-apply fixed it for me, but I had to enable and start the services post the reboot.
You may also try running the UpdateCas.PS1 as mentioned above.
-Praveen