Can´t Create New IOS simulator on Xcode

Try to restart the simulator service:

sudo killall -9 com.apple.CoreSimulator.CoreSimulatorService

This is likely because your app's target is set to a version higher than the simulator supports.

For example below:

a. After adding ios simulator 11.2 and adding an iPhone 5s while the app's target is still 12.2, you can see the simulators on lower OS version doesn't show up.

b. After changing target to 11.2

Added iPhone 5s now visible

Can you file a radar and include the output of sudo sysdiagnose -q and xcrun simctl diagnose? That last command might not work if you are on Xcode 8.2, in which case grab ~/Library/Logs/CoreSimulator/**. Also include the output of xcrun simctl list.

You should see some Simulators listed by default. The fact that you don't means there is something wrong with CoreSimulator or with Xcode's connection.

If simctl shows devices with no problems that is one thing. If it shows the default devices as unavailable then that is something entirely different. You can also run Simulator.app directly (Spotlight should find it for you) and see what devices it shows in the menu.

Close Xcode and Console.app. Run xcode-select -p and make sure it matches the location of Xcode, which should be /Applications/Xcode.app. If not, run sudo xcode-select -s <path_to_xcode.app>. Run sudo killall -9 com.apple.CoreSimulator.CoreSimulatorService. Then open Xcode and see if you can see the devices listed.

You might also try reinstalling Xcode if nothing else works. Each version of Xcode ships with a built-in Simulator runtime for each platform. In this case 10.2, meaning you should have a number of iOS 10.2 Simulators pre-created and ready to use.