And Welcome to the Spotify Community Actually something similar happened to myself before, but instead of the Error 500, what happened was that I was always being re-directed to the Browser page and I was never being able to click on a playlist page, that sucked. However in your case, there might be several possibilities, these are:
1) The Spotify server is not working fine at the moment and you have to wait for a while. (I do believe that of all the possibilities, this is the one that makes more sense)
2) You have some trojan attacking your PC doing that, on this case you might want to scan your PC using Malwarebytes.
Did you try to remove the /legal part of the page and reload it? It's cause I already tried to load the Webplayer with the /legal stuff in it and it seems the 500 Error does appear on my PC as well. Only without it, it works fine.
I guess it's all about patience (and persistence) after all...and if you want some feedback, I heared Spotify workers were kinda nice people, so why don't you give it a try? 🙂
Also, don't expect them to do anything unless you act and talk with them about your problems, it is you who have to start, not them. If you are expecting them to start, then I'm sorry to say this, you will have a frustrated waiting life.