I don't know if this is the right solution or it's just luck.
However here's what I did: I tried to setup the sandbox like everyone else, then I got that error, so after searching online I found out that a lots of users had the same issue and the solutions weren't logical at all, so I opened developer tools in Chrome, and I noticed that the website tries to get my profile picture, and because I don't have a profile picture it returns 404 error, so I uploaded a profile picture and it just worked.
Again this might just be pure luck, or right timing, but I just thought to share maybe it could help someone.