have you done a CTRL + F5? Have you tried inPrivate mode to enter Server manager? Sometimes you can get cached items stuck in the browser that block things.
If you have then my guess is that it's to do with the certs. I'd delete the CA signed certificates from portal and server, using portal/server admin, and then reload them.
There are times, and I'm not saying this is one, where AD policies enforce things in company browsers that make issues like this hard to resolve. Having a 'clean' laptop, if IT will let you have one may be a useful test.
Scott Tansley
https://www.linkedin.com/in/scotttansley/