What worked for me was to go to Programs and Features (appwiz.cpl), choose Turn Windows Features on or off, then check the box for .NET Framework 3.5 (Includes .NET 2.0 and 3.0).
I was getting the same error "Plugin DLL Defective. Reload." and "UC100 V2_151.dll - Defective Plugin Found..ignoreing.." on 64-bit Windows 10.
I used both driver options from the cncdrive website, and I had verified that the driver was installed properly, and that I had .NET installed (PowerShell reported 4.8.04084). The forums suggest that this DLL error is certainly related to .NET, so I'm guessing that while .NET 3.5 includes .NET 2.0 (required for the motion controller), higher versions do not. Making sure that .NET 3.5 was enabled included .NET 2.0, and now I'm in business!