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

I'm not sure what the underlying cause is, but I found I could successfully avoid this issue by closing down all running apps on the phone before trying to Run my code on my M8.