Please refer to this and provide help at either place.
https://stackoverflow.com/questions/46395095/dropbox-oauth2-authorize-400-error
Thanks, I'll try the workaround, but why is the endpoint from the documentation page still pointing to version1?
https://www.dropbox.com/developers-v1/core/docs#oa2-authorize
It shows:
https://www.dropbox.com/1/oauth2/authorize
That's the old API v1 documentation. I've updated my answer with the API v2 link. Thanks!
Thanks, this part works.