I suspected it was your folder structure, but when I copied it to my folder it didn't show up either. Do you have another file that does work? If so, I'd suggest opening it, editing the sketch to match this one, and "Save as" over this one.
I tried that, but SW said the file was Read Only, so I deleted it in Windows Explorer and then did a SaveAs Copy & Continue.
I think the outcome of that was the file I attached, actually.
I tried a SaveAs Copy & Continue to a different directory location and it worked!
I now have several sizes of pneumatic tubing safely in my weldments directory.
I have no idea what was wrong with the original directory structure, but it works now, so never mind!
Thanks for sending me down the correct path to look for a cure.