You must remove all age and country restrictions from your page in order to allow an app (using an App Access Token) to access your page and get the feeds.
If you can't remove those restrictions, you need to generate an access token and renew it automatically in the background:
Log into Facebook as a user who has admin permissions to the relevant Facebook page.
Then go to this link: https://www.facebook.com/dialog/oauth?client_id={your-app-id}&redirect_uri={a-link-back-to-your-website}&scope=manage_pages,publish_stream&response_type=token
This link will pop-up a confirmation dialog and will grant the "Manage Pages" and "Post" permissions to the app.
Once confirmed, the app from now on will be able to post and manage your pages using the access token that appears in the url of the redirect uri.
Save that access token for further use by your server.
Hope this helps.