I'm using Eclipse Luna with Activiti Eclipse BPMN 2.0 designer plug-in 5.15.0…
When a diagram is opened the grid doesn't show. Menu item View / Grid is checked. If you switch menu item View / Grid off and then switch it on again, the grid will be shown.
Is it issue of Activiti plag-in or Eclipse visual editor?
I am also using Eclipse Luna (so far I'm having no trouble with it). The grid doesn't show when I open Eclipse even though the box for it is checked. I just uncheck the box and check it again and voila: there's the grid 🙂 Maybe this does the trick for you as well.