Open button greyed out; can't open downloaded .skp files

On an Imac running OSX 10.9.4. I just downloaded SketchUp Make 2015 to view some .skp files I downloaded. When I double-click the file icons SketchUp launches, but the Open button is greyed out. Same thing when I drag the file to the Sketchup icon. I welcome any ideas on how to fix this.

do not double-click or drag’ndrop but try the classic “File > Open…”

if this doesn’t work this might not be true SketchUp files in native SKP format but files of another file format with the file extension renamed to “.SKP”.

On the dropdown menu, “File>Open” is greyed out.

Some OS’s consider downloaded files security risk and block them so you have to unblock. Have you checked file properties. (FYI I only have windows 7)
Can I assume you can start SU and run normally??
Can you attach one problem file here?

Most strange! Is the File->New also greyed out? What about other items on the menus? What about the icons on the toolbars? I’m probing trying to figure out what is wrong, as 2015 runs fine on lots of other 10.9 Macs…

Rank beginner. I clicked on the Start Using button and all the options in the edit menu became available. Problem solved. Thanks.