GregRout, I have the SAME problem! I go to the task bar to where all the notifications show up, I click the focus assist, and it WONT TURN OFF! Unlike you, I can't get it to shut off even for a few minutes or seconds. I then go to settings, disable everything, click focus assist off, AND IT DOESN'T DO IT! It is STUCK on focus assist. Personally for me I am very busy and need to receive important emails so this feature is TRASH. Before the Windows 10 update, I turned it on when working on something important, but now it WON'T TURN OFF!
Microsoft, Please send help!