Customizing AX 2012 Retail POS

Hello All,

I am trying to customize AX 2012 POS, I've installed Retail POS Plugins, I want to use the "Item" Service, When I compile the item assembly, and start POS with new item.dll, POS gives me error "Could Not Load All External Modules", I did not modify the add-in Class, just want to make sure it is compiling and working fine, so I can add my code in this, but it is not working, assembly is signed and all references are intact.

Please help.