I've got a bunch of open windows in Firefox and somehow two of them (this one included which is the most recent one I've opened) are isolated into their own group. The other 8 or so windows will cycle through when I hit the command-~ key, but this window and the other window in its group never come up and I have to use the mouse and Window menu to select one of those windows. After I select one of the windows in that other group, the command-~ key will cycle through just those two windows and ignores the other 8 windows. Are those different desktop spaces? How can I get all the windows to be in one group?
(I'm talking about browser windows only here. Each window might have any number of tabs in it, but that doesn't seem to be relevant.)
MacOS Sierra, Firefox 89.0 (64-bit)