Cannot minimize or close window in Windows 10

I’ve searched the forum and can find reference to something like this (or it may be like this) in Ubuntu. This problem just occurred randomly. My window was maximized to the full size of the screen and the close (x) and minimize [square] buttons were not there. I had to go into MS Task Manager to close the program to get control of my screen back.

Steps to reproduce

I don’t know… You can see that at the top right of the image there is no minimize or ‘x’.

Am using latest version…

Did you press F11 and went fullscreen?