I am consuming the instagram and have been able to sent the invite to my second user. However when the second user logs in to this link:
https://www.instagram.com/oauth/authorize/?client_id=XXXXXXX&redirect_uri=yyyyyyyyyyy://&response_type=token
they just get
{"code": 403, "error_type": "OAuthForbiddenException", "error_message": "You are not a sandbox user of this client"}
I have also logged in as that user to the official instagram app and still I have no place to accept the invite. How do the sandbox users accept their invites to use my app?