This is from Facebook:
Thanks for working with me to fix your app,[app name] (AppId: **********).
Your app is currently in violation of Facebook Platform Policy 8.3: Use a clearly branded “Login with Facebook” button and follow the Facebook Brand Guidelines.
This can be fixed by taking a look at our guidelines regarding the clearly branded login button. The shape and dimensions in this logo are compliant with our policies. Currently, your Login button doesn’t properly reference Facebook.
https://developers.facebook.com/docs/facebook-login/web/login-button
Your Login button doesn’t properly reference Facebook. To fix this issue, you should always use our official SDK for Login. For more information on Login best practices, check out the Login section of our developer documents: https://developers.facebook.com/docs/facebook-login/best-practices#buttondesign.
Please respond directly to this email after you have updated your app and we will do our best to assist you.