"Duplicate Canvas" is greyed out - any ideas why?

6.5, OSX 10.10.5, option is greyed out in a Stencil I’m trying to build for sharing at work - any ideas?

thanks :)

If using cmd D while the canvas is selected doesn’t work, please send in some details so we can help! OmniGraffle@OmniGroup.com

That doesn’t work either sadly - this is a copy of the Twitter Bootstrap stencil, I wondered if there was any sort of copy protection that was restricting things?

Thanks for the reply