When i try to test the ooauth/debug?_format=json endpoint through Postman i get the internal server error and error code 403 forbidden. Even though i use a valid Authorization header with Bearer and the access token for a certain user. The endpoint works fine for anonymous user. So i guess it's a permission error or the token expires even though i've set a big expiration date for testing purposes. Has anyone encountered the same issue as me? If yes did you manage to solve it? I follow the tutorial step by step from the official simple_oauth module page in drupal. Thanks in advance for reading this.
I fixed this issue by going to
admin/people/permissions and selecting all of the Simple OAuth permissions for Authenticated User. I'm sure a more refined approach to selecting permissions will be possible, but initially selecting all of them has fixed this issue for me.