title: Xamarin.Forms IOS Wont build
body: <p>I am getting the following error in Visual Studio:</p>
  
  <blockquote>
    <p>Severity Code Description Project File Line Suppression State
    Error 2016-11-10 08:12:21.588 ibtoold[1725:9661] [MT] DVTAssertions: Warning in /Library/Caches/com.apple.xbs/Sources/IDEInterfaceBuilder/IDEInterfaceBuilder-11542/InterfaceBuilderKit/Utilities/IBAbstractInterfaceBuilderPlatformToolManager.m:254
    Details: Failed to attach to Interface Builder Cocoa Touch Tool with error: Error Domain=com.apple.InterfaceBuilder Code=-1 "Encountered an error communicating with Interface Builder Cocoa Touch Tool." UserInfo={NSUnderlyingError=0x7f8f53b7e450 {Error Domain=NSPOSIXErrorDomain Code=22 "Invalid argument" UserInfo={NSUnderlyingError=0x7f8f53c086a0 {Error Domain=NSPOSIXErrorDomain Code=22 "Invalid argument"}, NSLocalizedFailureReason=Failed to spawn Interface Builder Cocoa Touch Tool on SimDevice : IBSimDeviceTypeiPad2x (4F7AF09B-A326-4A75-8657-3269C0EF6AE9) : state={ Shutdown } deviceType={ SimDeviceType : com.apple.dt.Xcode.IBSimDeviceType.iPad-2x } runtime={ SimRuntime : 10.1 (14B72) - com.apple.CoreSimulator.SimRuntime.iOS-10-1 }, NSLocalizedDescription=Failed to launch Interface Builder Cocoa Touch Tool via CoreSimulator spawn}}, NSLocalizedDescription=Encountered an error communicating with Interface Builder Cocoa Touch Tool., NSLocalizedRecoverySuggestion=Please check Console.app for crash reports for "Interface Builder Cocoa Touch Tool" for further information., NSLocalizedFailureReason=Interface Builder Cocoa Touch Tool (-1) failed to launch}
    Object: 
    Method: +_THREADSAFE_launchNewToolWithLaunchContext:executionContext:toolProxyClass:failureContext:requestingMethod:error:forReason:
    Thread: {number = 1, name = main}
    Please file a bug at <a href="http://bugreport.apple.com" rel="nofollow noreferrer">http://bugreport.apple.com</a> with this warning message and any useful information you can provide.
    2016-11-10 08:12:21.588 ibtoold[1725:9661] [MT] IBPlatformTool: *** Failed to launch tool with description System content 2x for IBCocoaTouchFramework-NineOneAndLater w/ default fidelity: Encountered an error communicating with Interface Builder Cocoa Touch Tool. (Failure reason: Interface Builder Cocoa Touch Tool (-1) failed to launch): Failed to launch Interface Builder Cocoa Touch Tool via CoreSimulator spawn (Failure reason: Failed to spawn Interface Builder Cocoa Touch Tool on SimDevice : IBSimDeviceTypeiPad2x (4F7AF09B-A326-4A75-8657-3269C0EF6AE9) : state={ Shutdown } deviceType={ SimDeviceType : com.apple.dt.Xcode.IBSimDeviceType.iPad-2x } runtime={ SimRuntime : 10.1 (14B72) - com.apple.CoreSimulator.SimRuntime.iOS-10-1 }): The operation couldn’t be completed. Invalid argument (Failure reason: Invalid argument)
    2016-11-10 08:12:35.502 ibtoold[1725:9661] [MT] IBPlatformTool: Wrote failed marshalling request diagnostics to path: /var/folders/tn/0v0_c5j95614q6vh8_blgjqc0000gn/T/IB-agent-diagnostics_2016-11-10_08-12-29_853000 InspectMobile.iOS</p>
  </blockquote>
  
  <p>and also</p>
  
  <blockquote>
    <p>Internal error. Please file a bug at bugreport.apple.com and attach "/var/folders/tn/0v0_c5j95614q6vh8_blgjqc0000gn/T/IB-agent-diagnostics_2016-11-10_10-13-47_446000".</p>
  </blockquote>
  
  <p>Sometimes this error doesn't happen but 99.99% of the time it does
  I have the following installed :</p>
  
  <p>on my windows pc</p>
  
  <ul>
  <li>Xamarin.VisualStudio_4.2.0.719</li>
  </ul>
  
  <p>on my Mac</p>
  
  <ul>
  <li>Xcode 8.1 </li>
  <li>xamarin.ios-10.2.0.4 installed </li>
  </ul>
  
  <p>I am trying to build to a emulator but I have also tried to build to a device, same error occures.</p>