After updated iOS 8 on mac OSX 10.9.4 using Xamarin 5.4 (build 240).
When run application on simulator application runs fine.
When I connect my device and run I got below error message.
Error MT5203: Failed to generate the debug symbols (dSYM directory). Please review the build log. (MT5203) (ProjectName)
before update Its run successfully on device and simulator.
This usually happens because you haven't agreed to the Xcode/iOS license.
It is easily fixed by launching Xcode once.