Why can't I activate the workbench Solidworks Add-In?

I don't have admin rights on my computer, so I got IT to install GrabCad workbench, including the Solidworks Add-In. The standalone GrabCad application works fine, I'm able to upload, download, etc.., but I can't activate the GrabCad Add-In in SolidWorks.
When I go to SolidWorks > Tools > Add-Ins, I see GrabCad (unchecked) in the "Other" section. When I check it and hit OK, nothing happens (no tab added to right side). When I go back into Add-Ins, it's unchecked again.
Any ideas?