IDB Launch App Error

IDBError

Xamarin.Messaging.Client.AgentConsoleRunner Information: 0 : [2016-08-16 22:56:35.9968] ==== :: Xamarin :: 4.2.0.495-cycle8+5920e67 ====
Xamarin.Messaging.Client.AgentConsoleRunner Information: 0 : [2016-08-16 22:56:36.0032] Starting IDB 4.2.0.495...
Xamarin.Messaging.IDB.IDBAgent Information: 0 : [2016-08-16 22:56:40.3266] Starting Agent: IDB 4.2.0.495 (PID=14505)
Xamarin.Messaging.IDB.IDBAgent Information: 0 : [2016-08-16 22:56:40.9532] IDB 4.2.0.495 agent started
Xamarin.Messaging.IDB.MTouch Information: 0 : [2016-08-16 22:57:55.5995] /Users/macbook/Library/Caches/Xamarin/XMA/Agents/IDB/4.2.0.495/mlaunch --devname "iPhone 6s" --installdev "/Users/macbook/Library/Caches/Xamarin/mtbs/builds/App20/f202e3f04783d316071ba68bb93139ca/bin/iPhone/Debug/App20.app" -argument=-monodevelop-port -argument=10000 -argument=-connection-mode -argument=usb --sdkroot "/Applications/Xcode.app/Contents/Developer" -sdk 9.3
Xamarin.Messaging.IDB.MTouch Information: 0 : [2016-08-16 22:57:57.5565] Installing application bundle 'com.companyname.App20' on 'iPhone 6s'
Xamarin.Messaging.IDB.MTouch Information: 0 : [2016-08-16 22:57:59.0234] Application bundle 'com.companyname.App20' installed on 'iPhone 6s'
Xamarin.Messaging.IDB.MTouch Information: 0 : [2016-08-16 22:57:59.2202] Process Exited
Xamarin.Messaging.IDB.MTouch Information: 0 : [2016-08-16 22:58:00.2232] MTouch Run Terminated
Xamarin.Messaging.IDB.MTouch Information: 0 : [2016-08-16 22:58:00.2282] /Users/macbook/Library/Caches/Xamarin/XMA/Agents/IDB/4.2.0.495/mlaunch --devname "iPhone 6s" --killdev "/Users/macbook/Library/Caches/Xamarin/mtbs/builds/App20/f202e3f04783d316071ba68bb93139ca/bin/iPhone/Debug/App20.app" --launchdev "/Users/macbook/Library/Caches/Xamarin/mtbs/builds/App20/f202e3f04783d316071ba68bb93139ca/bin/iPhone/Debug/App20.app" -argument=-monodevelop-port -argument=10000 -argument=-connection-mode -argument=usb --sdkroot "/Applications/Xcode.app/Contents/Developer" -sdk 9.3
Xamarin.Messaging.IDB.MTouch Information: 0 : [2016-08-16 22:58:02.3692] Launched application 'com.companyname.App20' on 'iPhone 6s' with pid 291
Xamarin.Messaging.IDB.MTouch Information: 0 : [2016-08-16 22:58:02.4672] Process Exited
Xamarin.Messaging.IDB.Handlers.LaunchAppMessageHandler Information: 0 : [2016-08-16 22:58:02.5534] Connecting debugger on 51917
Xamarin.Messaging.IDB.MTouch Information: 0 : [2016-08-16 22:58:03.5367] MTouch Run Terminated
Xamarin.Messaging.IDB.Handlers.LaunchAppMessageHandler Information: 0 : [2016-08-16 22:58:07.3647] Closing from TCP
Xamarin.Messaging.IDB.Handlers.LaunchAppMessageHandler Information: 0 : [2016-08-16 22:58:07.3722] Closing from USB
Xamarin.Messaging.IDB.Handlers.LaunchAppMessageHandler Error: 0 : [2016-08-16 22:58:07.3954] One or more errors occurred.
System.AggregateException: One or more errors occurred. ---> System.NullReferenceException: Object reference not set to an instance of an object
  at Xamarin.Messaging.IDB.Handlers.LaunchAppMessageHandler.<CreatePhysicalDeviceUSBConnection>b__18_1 (System.Threading.Tasks.Task t) [0x0000b] in <2905a2cfbb844ff79c4a7e16e559ee29>:0 
  at System.Threading.Tasks.ContinuationTaskFromTask.InnerInvoke () [0x00027] in <cb2113739f1e4ff7a48a90c180b42f45>:0 
  at System.Threading.Tasks.Task.Execute () [0x00016] in <cb2113739f1e4ff7a48a90c180b42f45>:0 
   --- End of inner exception stack trace ---
---> (Inner Exception #0) System.NullReferenceException: Object reference not set to an instance of an object
  at Xamarin.Messaging.IDB.Handlers.LaunchAppMessageHandler.<CreatePhysicalDeviceUSBConnection>b__18_1 (System.Threading.Tasks.Task t) [0x0000b] in <2905a2cfbb844ff79c4a7e16e559ee29>:0 
  at System.Threading.Tasks.ContinuationTaskFromTask.InnerInvoke () [0x00027] in <cb2113739f1e4ff7a48a90c180b42f45>:0 
  at System.Threading.Tasks.Task.Execute () [0x00016] in <cb2113739f1e4ff7a48a90c180b42f45>:0 <---

Xamarin.Messaging.Client.AgentConsoleRunner Error: 0 : [2016-08-16 22:58:13.3316] An unexpected error occurred and the agent 'IDB 4.2.0.495' will be terminated
System.IO.IOException: USB stream error: EBADF
  at Xamarin.MacDev.IPhoneUsbStream.Read (System.Byte[] buffer, System.Int32 offset, System.Int32 count) [0x00077] in <9e61d804c9d045a2bd9258e7b4efdb4e>:0 
  at Xamarin.Messaging.IDB.Handlers.LaunchAppMessageHandler+<>c__DisplayClass19_0.<ConnectOutput>b__0 () [0x0004b] in <2905a2cfbb844ff79c4a7e16e559ee29>:0 
  at System.Threading.Tasks.Task.InnerInvoke () [0x00012] in <cb2113739f1e4ff7a48a90c180b42f45>:0 
  at System.Threading.Tasks.Task.Execute () [0x00016] in <cb2113739f1e4ff7a48a90c180b42f45>:0