I tried "Reset Layout" in the Mechanical window.  The blank content area moved from the right side of the window to the left for a couple seconds, then moved back, but otherwise everything is the same.

I tried opening a new project and then a new Mechanical Model.  That works fine, but there is still nothing in the content window.  I think there should be a ruler and an x/y/z arrowhead, but those aren't there.  I'm an IT guy, so I don't know what to do with it beyond that.

Do you have a known-good sample project with a Mechanical model that I could download and try?