This error is caused by the fact that IDKit.dll library is missing on the system where you are running your application. Please install IDKit PRO SDK on the computer where this error is occurring or copy the IDKit.dll (from IDKit PRO SDK) into \Windows\System32

The library Innovatrics.IEngine.dll is just .NET wrapper of native IDKit.dll library. Therefore you have to distribute both IDKit.dll and IDKit64.dll (in case of 64bit system) with Innovatrics.IEngine.dll.