Focus Assist in Windows 10 not working and Settings crashing

I am writing this post to let people know why a particular annoying problem happens on Windows 10 with regards to notifications. Before it was called "Focus Assist" it was called "Quiet hours" and you would turn it on to make annoying notifications not show while you were working or playing. After a Windows update, Microsoft renamed it to Focus Assist and turned it into a more complex setting, rather than on/off. But then the problems appeared.

Symptoms:

• Notification traybar bubble is white (outline filled) and going over with the mouse it either says nothing or says "1 notification"
• When you click on it, it shows no notifications and the bubble remains filled
• If you right-click it, none of the options in the Focus Assist menu seem to be working and none are checked
• If you go to Settings and click on Focus Assist, Settings crashes with no error message
• You also may have Avast antivirus installed

People have been tracking the problem on this Microsoft forum: Settings app crashes accessing "Focus Assist" settings and here are our findings:

1. The problem comes from Avast (or some other source) turning off the Windows Push Notifications User Service. Turning it on, restores Focus Assist functionality.
2. Avast has something called Silent Mode, which many people use because Avast started pushing all these annoying messages lately
3. In the Avast configuration (go to Menu , Settings, Components, scroll down the page until Performance, Do Not Disturb Mode, then Customize) there is a setting called "Silence notifications from 3rd-party apps". By default it's on. Turn it off and Avast will no longer kill the service
4. If the cause of this behavior is different from Avast's silent mode, let me know. An immediate fix is to go to Services (services.msc), scroll down to Windows Push Notifications User Service (followed by underscore and some meaningless numbers and letters) and make sure it is started.

Hope this helps.