Hm. And you’re not trying to make a raw request to the API outside of the app, correct? You need the token provided by the Rails app.
If not, I might suggest we double check the versions of the two apps that you’re running. The latest version of Annotation Studio (master branch on github/hyperstudio) stores the jwt in the user session, and if/when that expires, all requests to the API will fail. Quick fix for that issue is to logout/log back in.
I would be glad to jump on a google hangout if that would be useful.