When I tried to run the app in simulators, I hold Xcode 8.3.2 and Xcode 9 beta 1 and my project was running in Xcode 8.3.2. I got the below errors.
Images.xcassets: error: Failed to find a suitable device for the type SimDeviceType : com.apple.dt.Xcode.IBSimDeviceType.iPad-2x with runtime SimRuntime : 10.3 (14E269) - com.apple.CoreSimulator.SimRuntime.iOS-10-3
Failure Reason: Failed to create SimDeviceSet at path /Users/Mac/Library/Developer/Xcode/UserData/IB Support/Simulator Devices. You'll want to check the logs in ~/Library/Logs/CoreSimulator to see why creating the SimDeviceSet failed.
Underlying Errors:
Description: Failed to initialize simulator device set.
Failure Reason: Failed to subscribe to notifications from CoreSimulatorService.
Underlying Errors:
Description: Error returned in reply to notification request: Connection invalid
Failure Reason: Software caused connection abort
/* com.apple.actool.document.notices */
For me it did not help cleaning. I had to run sudo killall -9 com.apple.CoreSimulator.CoreSimulatorService and then I was able to start the app via the Simulator