It’s happened because your app on Facebook for developers website is not active
solution
- go to Facebook for developers from here
- choose My Apps from the top bar
- click on your app icon ( then you will notice that your app is not active from the top bar )
- from the left side select settings >> basic
- put your privacy policy link in the Privacy Policy URL and in the User data deletion field, you can make a copy from this privacy policy ( to make a copy from the privacy policy select file from the top bar and select make a copy )
- press save changes
I hope that it was helpful