I tried to log on to Pokemon showdown today and everything never stop saying loading. I know my internet is good so why is this.
The devs of Showdown are already working on this, just wait. There's not much you can do.
SewerRat1 also has another way to try and fix it:
So I found a fix to this. You have to erase all your website data. It’s very inconvenient but it worked for me and I was able to play the game again like normal. Just don’t forget to back up your teams if you can. I forgot to and lost all my teams
Edit: Mia has fixed the problem.
It looks like I've fixed the issue. Hard refresh (Ctrl+F5 on Windows, Cmd+Shift+R on Mac) to clear your cache and receive the new client changes.