Since the latest change on Facebook, regarding the appsecret_proof: https://developers.facebook.com/docs/reference/api/securing-graph-api/, we are still unable to download p
Perhaps something wrong with your access token, you need Business Manager style.
You can get the token from the content of https://business.facebook.com/settings/system-users/{sys_user_id}?business_id={business_id} with regex r'"accessToken":"([\d|\w]+)","context"'