Unable to test app after upgrading to Lollipop

Question

I am using Android Studio to develop my apps.

Since I upgraded my HTC One M8 to Lollipop, I can not use it to test my apps by \"Run app\" in Android Studio. I get

Answer 1

This solution worked for me, you may give it a try.

Add adb path to System Environment Variables (I'm using windows 8)
Ex: my path is "C:\Users\xxx\AppData\Local\Android\sdk\platform-tools"
Dont forget to reboot your system to take the effect!

About how to set the path and environment variables in Windows >> here