Microsoft 365 Unable to create new email

It's MUCH more interesting and stupider than that.....................
Up until THIS MORNING, when I press the "New Email" button, I get a new email in the Outlook pane with the list of other emails - the normal email in the bottom of the normal Outlook Window...

THIS MORNING, instead of opening the new email in there, it created a SEPARATE DOCUMENT and stuffed it in the far corner of the second monitor.... BEHIND all the OTHER stuff on that monitor that are THERE because they're things I don't need all the time and rarely look at...

So, TO ME, there WAS no NEW EMAIL... I spent 2 hours, reboots, clobbered the whole MS365 installation, and THEN realized there WAS a document being created - I could SEE it with the Outlook icon on the taskbar, BUT NOWHERE ELSE.

NOW I just need to figure out HOW to get Outlook to go BACK to putting the NEW Email in the normal Outlook pane like it's done for the last umpteen years - until this morning........

Update:  OK, I have NO IDEA how to get this email back into the normal Outlook pane with my folders on the left and the emails in lines on the right at the top, and the big empty space on the bottom right where the new email I was creating USED to show up...  I knew how to do it int Outlook 2019, but I have no idea how in Microsoft 365.  I'll keep fumbling around, but...