User Profile

For some reason when I go through the same process as shown here: https://developer.apple.com/documentation/musickitjs/ using MusicKit JS to authorize a user, the popup opens a user logs in and then on the access request screen you click allow nothing happens. You can see in the network tab when inspecting that the usertoken is being generated but the popup isn't closing and no matter what I try I cannot extract the usertoken, any thoughts?