Startup hanging at 'Verifying mysql Database Connection'

Version 0.48.4

I had a failed attempt to upgrade to 0.49, so rolled back both my database server and metabase server to a backup from last night.
Now, the site never completes startup. If I run from command line, I see no errors but it stops at:

The MySQL database is definitely running as I can connect to it from another server.

Nothing has changed so I'm just confused. Any thoughts on best approach to troubleshoot?

RAM, what's the amount of RAM? that happens either due to RAM exhaustion or entropy exhaustion

I doubled the RAM and still fails. I'm tempted to rip and replace. Will give me a good opportunity to try out containers on Azure.

You couldn't make this stuff up - my Azure subscription has gone haywire and I can no longer create resources! I've emailed MS, so hopefully resolved soon.

Kicking myself. The Metabase server didn't have a fixed IP address. It's never changed while rebooting in the past, but has done now.
I've changed the Azure firewall and the MySql account. all working now.