Same thing happened to me even after updating to 18.6.2 and then I solved it (I think).
Swipe from upper right corner down on your main screen.
Open focus.
Four tabs appear
Do Not Disturb
Sleep
Reduce Interruptions
Driving
If it shows
Do Not Disturb ON
Just tap it and it changes to
Do Not Disturb "silence all notifications"
That should mean it's off now.
So with all those tabs you just tap once to turn on or off.
I guess they "simplified" things and we're supposed to intuit the new rules?
I hope that works. It was driving me nuts all morning.