Web Page Not available

After installing the APK it show a screen with the following message:
Web Page not available
The web page at http://mysite.com/?WordApp_Mobile_app=app might be temporarily down or it may have moved permanently….

My site is still there and there is no problem in the server or internet connection and the plugin is obviously active.
Could any one please help?

https://wordpress.org/plugins/wordapp-mobile-app/