Unable to access the GUI after changing the Ip address

No error from firefox, after going through the "insecure" dialog, it just gives me a blank screen.
any errors in the developer console?

do you have any plugins on your firefox?

could you try with an incognito window (without plugins)?
 
I was having the same problem, after editing the IP address from 192.168.1.8 to 192.168.1.10, I was getting an error where I couldn't login to the web interface, or I can get in but none of the GUI was working. I previously had another pve server with 192.168.1.10, and the new hardware was temporarily being setup as 192.168.1.8. Once I was ready, I shutdown the 192.168.1.10, and then changed the IP address of the new server to 192.168.1.10 and was having problems.

I did some "systemctl restart pvedaemon pveproxy" and also system reboot as suggested from the thread, but it didn't make much change. Trying a different browser, I found that my previous pve server certificate was stored in Chrome and that was interfering.
So in the end, I had to copy the new certificate from /etc/pve/nodes/{my-server-name}/pve-ssl.pem and import that as a custom certificate in Chrome (chrome://certificate-manager/).