How to Fix ‘APPLICATION NOT INSTALLED’ Error on Tecno and other Android phones - It’s the annoying error message you hate seeing on your Android phone: “Application not installed”. What happened? All you were trying to do was install an Android app. That should be simple.
Receiving this error message is a common problem when downloading APK files. APK stands for Android Application Package, and it used by the Android operating system as the package file format for the installation and allotment of mobile apps.

If for some reason, your Android device is unable to access Google Play, APK files offer another option for installing and downloading mobile apps. APK files are designed exclusively for Android devices.

Before getting into the details of the ‘Application not installed’ error message, let’s take a look at Android and its development and success over the years.

Please view Detailed Solutions here http://www.tecnomobiles.com/2017/01/quickly-fix-application-not-installed.html