Error on file load "not the right kind of document"

Created several versions of a project. Of the six, one will now not open--when I try, I get the message, "Could not complete your request because it is not the right kind of document." The icon shows as a PSD file, and when clicked it will try and open in PS, but in the file details, instead of  Type of file: Adobe Photoshop Image.21 (.psd) it shows as Type of file: 1 File (.1).

Anyone seen this before? Any info at all would be appreciated. I've got about four hours of work locked in that file that I'd like to get back.

I'm running the current ver of PS on a Dell T3500, 3.2 ghz xeon, 12gb ram, windows 10pro, Nivida Quadro K4200

Thanks.