Mannequin does not load in Maya

I am trying to add the A.R.T. mannequin into my scene but when I click to “add character for animation” it tells me Error: there are no characters in scene, add characters now? When I click yes nothing happens. If I do the same thing with a sample rig I created in UE4 it works just fine but I need the mannequin specifically for a project. Any help is appreciated. Thanks!

have the same issue.
tried to open the Mannquin maya file directly didnt work either.

// Error: line 1: Unrecognized file. //
in command window.