Also, I'm not just having the "it doesn't work" issue switching between open excel files. I'm also having the same problem switching between open programs (Firefox, Quickbooks, adobe, excel...). Sometimes clicking on the icon on the taskbar results in the program showing up on my monitor. Sometimes it doesn't. Sometimes alt-tab through all my open programs and stopping on the one I want to see results in the program showing on my monitor, sometimes it doesn't. When neither of those work, sometimes I can minimize everything thing and try one of the above and what i want to see shows up on my monitor, sometime it doesn't.
Basically Windows 11 doesn't seem to be working consistently, as far as I can tell?