Ionic Push - XMLHttpRequest cannot load https://apps.ionic.io/api/v1/app/34637fe7/users/identify. Request header field If-Modified-Since is not allowed by Access-Control-Allow-Headers

ionic-v1
1

I was able to get the tutorial app working for Ionic Push but when I put the code into my app, I’m getting the following error:

XMLHttpRequest cannot load https://apps.ionic.io/api/v1/app/34637fe7/users/identify. Request header field If-Modified-Since is not allowed by Access-Control-Allow-Headers.

The errors seems to happen when I called $ionicUser.identify

Any ideas why this is happening?