: The APK file might be corrupted or for a newer version of Android. Re-download the version specific to Android 5.1.
The problem? The tablet had no Google Play Store. Just a barren desert of pre-installed apps from a brand nobody remembered. how to install google play store on android 5.1.1
Check via an app like Droid Hardware Info or run getprop ro.product.cpu.abi in a terminal. : The APK file might be corrupted or