Hello:
My app works perfectly in my cell phone. But, when trying to run it in an tablet, I am receiving a runtime error message (please see attached screenshot). Any help would be highly appreciated.
You had a similar issue with your Android 4.4
H5P quiz from Wordpress not displaying on a tablet .
Are you trying to use html5 (H5P) . Your tablet needs HTML5 in a Webviewer. This means your tablet should be at least Android (5.1+) to support html5.
It seems your Android tablet is too old to support some of the code in your app, 
Thanks, Steve. You´re probably right, although my tablet system (old Android 4.4) was updated to 7.1 by using a non official tool. I´m afraid this updated version is not strong enough.