The Android Package Manager error INSTALL_FAILED_SHARED_USER_INCOMPATIBLE triggers when updating an APK whose android:sharedUserId tag or signing certificate mismatches existing installed app data.

ADB Full Uninstall Command

ADB Commandbash
# Uninstall conflicting app package completely before re-installing
adb uninstall com.example.myapp
 
# Force install app with updated sharedUserId
adb install -r myapp.apk