I have the same problem, it won't open, tried installing latest version, still won't open.

What freaking use is this?

Worse, I cannot find any sign of any file ending in ".wallet". Does the backup have a different file extension or should I be able to find it with a wildcard search for *wallet?

Hidden folders and files IS switched on.

I know I have a paper backup for 0.5 of a BTC (though I've entirely forgotten how to use it) but I should have 1.5 BTC in my main wallet, wherever the heck it is.

*sigh*