Workaround for loading issues when on cellular data mode:
  1. Open settings app.
  2. Select cellular option.
  3. Scroll down until you see the app having issues. 
  4. Make sure the switch on that app is set on (green.) This allows or disables cellular service.

Note: Supposedly there was a version of iOS that disabled this option on apps that were installed on that specific version. Unloading and reloading the app remembered the setting.