Killing the simulator and restarting it from Xcode helped me.
You are probably using macOS Sierra which breaks Xcode 7.3.1 (mac store version)
Use Xcode 8 beta or Xcode 7.3.1.dmg downloaded from the Mac Developer portal for a fix https://developer.apple.com/downloads
Direct link to Xcode 7.3.1: http://adcdownload.apple.com/Developer_Tools/Xcode_7.3.1/Xcode_7.3.1.dmg