App not installed can be caused by the following :
1. Incorrect file
If you already have an App installed but download another variant of it having a distinct signed or unsigned certificate can also make the Android App not installed error to pop-up. This sounds technical.
2. Corrupted/Contaminated App file
You should be doubly sure of the source from where your downloads of Apps are saved on the phone storage. check its extension name and make an effort not to install contained files.
3.Gradle file – The problem might be in the file itself. Just check the minimum SDK version is suitable for your device.
SOLUTIONS
Clear Data and Cache of Package Installer
- Open setting on your Android device.
- Look for the option called Apps or Manage apps and tap on it.
- Check for the Package Installer App under system Apps
- You will find two option of Clear data and Clear cache. (For Android Marshmallow 6.0 users check for option Storage to clear data and cache)
- Clear the data and cache to solve the problem.
For Root Devices
If you have a rooted phone than the success rate increases manifolds.
- Download and open any root explorer app on your rooted device.
- Copy the Apk then go to system >app and grant permissions to the app.
- You will see App installed on your device.
Using Lucky Patcher
- Download, install and open Lucky Patcher.
- Tap the option Toolbox
- Click Patch to android
- Check “Signature Verification status always true” and “Disable apk Signature Verification” and Apply.
- Reboot your device if not automatically rebooted.