I had another one come in from Fiverr:
Greetings my name is —, administrator of —.com. Im in need of a Wordpress & Website management professional. My sites —.com - —.com are both offline. I use A2 Hosting. I was in the process of doing 2 things, updating the PHP from 7.3 to 8.3, but when I did that both sites went down. I get a ‘There has been a critical error on this website.’ I switched it back to 7.3 but the error remained. Im also in the process of switching my website from Shared Hosting on A2 Hosting to Managed VPS Hosting. The Hosting company migrated the data but did a bad job, having broken links and etc. Would you be able to assist?
My fix was simple: Migrate to WPEngine. Doing this proved it was host related.
In order to accomplish this I had to do a bit of investigation inside via the CPANEL, PHPMYADMIN etc.
I then captured the MYSQL database and just the wp-content folder and everything inside. I manually migrated over the site to WP Engine.
Once migrated to a staging site the site came back to life with PHP v 7.4.
Really, these massive hosts or hosts that do anything other than “WordPress” should be abandoned. In this case, something about the PHP upgrade got stuck. Support was absent.
Then, magically A2 support provided the fix as this person was about to migrate away 
(retention department)