Facebook Meta Tags for Custom Domain in Heroku

Question

I have a Heroku app example.herokuapp.comwith these meta tags:

  <meta property='og:type' content='website'/>
  <meta property='og:title' content='MyApp'/>
  <meta property='og:image' content='https://example.com/_n.png'/>
  <meta property='og:description' content='This site is awesome'/>

Therefore, when I exchange example.herokuapp.com on Facebook, this data is displayed correctly. However, I set up my own domain on Heroku ( example.com), adding a CNAME (alias)pointing to example.herokuapp.comand adding a domain on Heroku.

Now when I submit example.com to Facebook, no details are displayed.