API Version

Thanks, that's helpful. Ok, so it looks like you're using the Android Core SDK. That presumably means you're using either Eclipse or Android Studio. In either case, when you use mDBApi to make an actual API call after all of the setup you have here, if something went wrong it would raise an exception with specific information about the issue.

I don't see where you make an API call using mDBApi in the provided code (presumably you do that later?), but I do see what I suspect is the issue. Specifically:

    String key    = mPrefs.getString("dropboxAuthKey", null);
    String secret = mPrefs.getString("dropboxAuthSecret", null);
    ...
    AccessTokenPair access = new AccessTokenPair(key, secret);
    mDBApi.getSession().setAccessTokenPair(access);             

It looks like you're retrieving a pre-existing access token, presumably for the old app. Since access tokens (the dropboxAuthKey and dropboxAuthSecret pair in your code) are specific to apps, you'll need to get a new access token for the new app key/secret.

If that doesn't seem to be the problem, e.g., if the code isn't going through that code path, please copy the relevant output you get when you run this. E.g., from logcat.