From the heart

Error: (#100) Object does not exist, cannot be loaded due to missing permission or reviewable feature, or does not support this operation. This endpoint requires the 'pages_read_engagement' permission or the 'Page Public Content Access' feature or the 'Page Public Metadata Access' feature. Refer to https://developers.facebook.com/docs/apps/review/login-permissions#manage-pages, https://developers.facebook.com/docs/apps/review/feature#reference-PAGES_ACCESS and https://developers.facebook.com/docs/apps/review/feature#page-public-metadata-access for details.
Type: OAuthException
Code: 100
Please refer to our Error Message Reference.