The offline access display is often flagged if you have previously granted an app access, but the app is asking for sign in again (if the consent dialog is being forced or similar). This is due to incremental auth - its trying to hide previously granted scopes.
To test this, try revoking all app access with https://security.google.com/settings/security/permissions and signing in again. You should see the full scopes.
If that is the issue, then it is likely something your users wont see - when they sign in again they should not see a consent dialog unless you are using prompt=force or similar.
You might also want to look at retrieving profile using the Google+ API (this works for all account types): https://developers.google.com/+/api/latest/people/get, and upgrading to the latest version of the PHP library: https://github.com/google/google-api-php-client