I got this problem in India. Try using VPN. I tried USA and Netherlands VPN and it did work.
If you look at the console errors and the network tab, some resources are failed to load. Using VPN, browser loaded those resources just fine for me. Try refreshing 1-2 times if you still can’t make it work. On using VPN, warning messages should change, hopefully!
Optional: If page loads on VPN, try to switch it off and access the control panel on your home network. Now page should load just fine on home network as well. You should be able to browse the control panel now. If not, try to refresh the page normally 1-2 times (don’t hard reload). If it does work, make sure you don’t hard reload the page or delete the cache.
Optional: You can try to switch on/off Enhanced Tracking Protection. In my case, tracking protection wasn’t the issue.