Looks like we can not directly use the apk after running on the device from the build->output->apk folder.
After upgrading to android studio 3.0 you need to go to Build -> Build
Apk(s) then copy the apk from build -> output -> apk -> debug
Like this –
Fist Click On Build Icon on android studio after that click Build APK(s)
then Generate APK the copy Apk.
It is working perfact.