Implicit grant flow

I have an old desktop app that uses implicit grant to authorize users. It worked until yesterday, now when the user puts his email and password, as soon as he authorizes my app, Dropbox doesn't put the access token in the URL that was redirected. I did a test by opening the authorization address manually through the browser, and at the end the URL shows just the redirect URI without the token.

My app is properly authorized, but I don't have the access token to perform the necessary actions.

Is it a transitory Dropbox problem or something?