The "App not installed" error on some mobile phones can occur due to various reasons. Here are some common causes and potential solutions: ### 1. **Insufficient Storage Space** - **Cause**: The device may not have enough storage to install the app. - **Solution**: Free up space by deleting unused apps, photos, or other files. ### 2. **Incompatible App Version** - **Cause**: The app might not be compatible with your device's operating system or hardware. - **Solution**: Check if the app is compatible with your device. Try downloading an older version of the app if available. ### 3. **Corrupted APK File** - **Cause**: The APK file you are trying to install might be corrupted or incomplete. - **Solution**: Re-download the APK file from a reliable source and try installing it again. ### 4. **Unknown Sources Not Enabled** - **Cause**: If you are installing an app from outside the Google Play Stor...