Invalid Device State - Xcode/iOS Simulator error

Force Quit xCode and restart will resolve problem.

I had come across this issue after updating Xcode 6.4 to 7.1. Below are fixes for this :

1. Clean project (cmd+shift+k) as well as clean build folder (cmd+shift+k+option)

2. Quit simulator and run again
3. Quit Xcode and Simulator and run again
4. Restart your Mac.

Solution 3 worked for me!

I had the same issue. Generally it is because you just update Xcode or change its name in the Applications folder.

If you just restart your computer it will work correctly.

Hope it helps !

I observed this happening when more than one Xcode app installed.

To fix this,

1. Launch Xcode and click preference..,
2. Go to "Location" Tab, Select correct options from "Command Line Tools" dropdown
3. Quit Xcode and relaunch it.
4. Run your app.