Dropbox Scoped App issues

Thanks for writing this up!

Regarding the app folder creation: the actual app folder in a connected account does not get created until the account is connected to the app. That is, just creating the app registration won't automatically create the app folder itself. That occurred when you generated a token because that was the first time the app was actually connected to your account as a user of the app. 

Regarding the 'Bad Request' error: make sure you print out the HTTPS response body itself, as it will contain more specific information about why the call failed. In this case, it sounds like it was likely because you didn't have the necessary scoped enabled for the app.

Regarding the 'missing_scope' error: Just enabling a particular scope for an app does not retroactively add authorization for that scope to existing access tokens. You'd need to process the authorization flow (either the OAuth flow or using the "Generate" button) again to authorize an access token with any newly enabled scopes.

Regarding the "You must be a team administrator to perform this operation." error:  That indicates that you selected one or more "team" scopes, which can only be authorized by a team admin. Also, note that the 'files.permanent_delete' scope automatically requires the 'team_data.member' scope, so you can't use 'files.permanent_delete' from a non-team account, and so enabling the the 'files.permanent_delete' scope will also cause that.