Native linking failed - IOS 12 Beta

I'm trying to compile my xamarin project and getting these errors:

**clang : error : linker command failed with exit code 1 (use -v to see invocation)

MTOUCH : error MT5211: Native linking failed, undefined Objective-C class: DTDeviceDelegate. The symbol 'OBJC_CLASS$_DTDeviceDelegate' could not be found in any of the libraries or frameworks linked with your application.

MTOUCH : error MT5202: Native linking failed. Please review the build log.**

Trying many ways following the stack overflow discussions. But still can't fix.