Unsupported get request in Facebook Graph API

This error occur due to several problem in permissions of your page

1. go to edit page ->manage permission

check Age restrictions : 13+

2. go to basic information -> Start Type:: set to launched

I had also encountered this problem, and it was because the Facebook page I was managing had "County Restrictions" set in the Manage Permissions menu. Once I removed this restriction, the graph error went away.

The page you are having trouble with is not accessible without user access token or has some or the other restrictions which are resolved only when a user logs in.