Is your forum behind a Content Delivery Network such as CloudFlare?
No. It's running on a linux box. It was running on a virtual private server, and I wanted to try it in a different environment before asking for help.
What does a hard refresh (Ctrl F5) show after attempting to login?
Hard refresh has no effect. I've also tried it in private browser windows. I've tried in Firefox and Chrome.
I was logged in as sysop after the upgrade finished The next morning, I couldn't log in.
Interestingly, some of my students who had been logged in before the upgrade, remained logged in after this started happening. No one else could log in.
fwiw, I also tried changing to the default stylesheet, since I was using a custom one. Still couldn't log in.
