If the other stuff mentioned didn't work you could also try to turn off your modem/router for 30 seconds and turn it back on and see if it works.
Hmm it still happened for me too sometimes with Era. Not really sure what causes it to go to that black screen.
Well...I can't login to classic with Opera or google chrome browser. I am getting the same issue where it shows a black screen after the loading page loads for an abnormal amount of time.
I can access classic with firefox though so I highly recommend trying to use as many browsers as you can until you can login.
Something happened like this to me recently Era where I couldn't login to Era at all using my wifi. I could connect using my phone's mobile data but It just wouldn't connect with my wifi. I think my ISP blocked me from connecting to Graal (Possibly because I always afk my accounts). I tried contacting my ISP for hours and they kept giving me random useless answers that didn't resolve the issue.
I was able to fix it by unplugging my modem/router and driving to my ISP (Comcast) and they gave me a new one for free in exchange for my old one.