Reference Assembly failed to load.

Hey guys, 

I'm currently working on building the Elvis robotic arm by suryansh chandra. A 6-axis desktop robotic arm control using grasshopper with Dynamixel Ax-12a Servos.

I'm having a problem loading the reference assembly Robotis.dll file. 

Attached is the current issue im having. 

Not sure what's the solution to resolve this.

Thanks in advance.