For what it's worth, I'm also experiencing this.

You wouldn't happen to be using Millenium and a Steam Skin, would you?

Nope just default clean install of steam, even did a fresh reinstall to no avail. I don't have another PC to test it so thank you for chiming in and letting me know this is at least not an isolated issue

Let's hope more people will find this thread, for now I have "fixed" it by changing the overlay taskbar to a menu, it's easier to find while hovering your mouse over, and clicking the taskbar reveals it (for me) so at least I got functionality back even if it's bugged

Having the same problem still

Almost same problem. When i click on place, where opened window in overlay was, it become visible

Same issue here.