What does the this Windows 10 Action Center tray icon overlay indicate, exactly?

Here is a screenshot, containing the icon (the one in the middle, presumably describing a text note, with what looks as a stop sign at lower right corner of it):

I cannot find explanation on what is being communicated to me here? Most of the time the icon does not have the stop sign overlay there, but regardless of this, clicking on it simply gives me the Action Center pane that says "No new notifications".

So, what could that overlay indicate? I am not the worrying type, but I am an IT specialist, so I want to know what's going on.

Solution 1:

It indicated Quiet hours enabled (even if you didnt enable them = bug). Turn on and off Quiet hours and icon should disappear.

Solution 2:

The stop kind of symbol on the Action center originally means Quiet Hours are enabled. so if your PC shows that symbol even if the Quite hours are not enabled, then try enable and disable it. it should solve your problem. Thank you.