Session 'app' error while installing APK

Question

I am having difficulty importing a project written on Android Studio 1.1 into Android Studio 2.1.2. I keep getting this error whenever the gradle is building before testing

Answer 1

Try to this way :

1) In Instance Run is Enable then desable it. 2) Save it and Rebuild the project. 3) Check devices is online or USB debugging On your device. 4) Then Run It App On your devices.

Note :

If you use mobile device is MI (Xiaomi) Then Check : => setting>Additional setting> Developer options> Install via USB (ON it) => setting>Additional setting> Developer options> USB debugging (ON it) => setting>Additional setting> Developer options> Verify apps over USB (ON/Off it)