There is a bug where it doesn't display on the active screen. I clearly click inside my primary screen (the one right in front of me), and the task switcher still shows up on my 2nd monitor. This may be caused by the fact that I was clicking inside my Firefox window in my primary screen. There is a 2nd Firefox window on my 2nd monitor, so perhaps the functionality that is checking what my active monitor is, isn't registering this correctly since there are 2 firefox windows, 1 on each monitor? Pure speculation, but it might help.

I split your comment into a separate thread, please do not use threads older than a 12 months and about obsolete versions (this was over 6 years old and clearly about a completely different version).

FWI: see red text in my signature...