hello it's late but i'll explain to you what is the problem : https://developers.facebook.com/docs/pages-api/getting-started/#-tape-1--obtenir-l-id-de-votre-page-2
you have to get your access_token of page id with https://graph.facebook.com/v22.0/{user_id}/accounts
in your response you will have access_token.
You have to use this token not the user token.
Hope that will help some one