Running Cura 3.2.13 in Debian GNU/Linux (Stretch)
Opening up Cura, it automatically displayed a question mark next to the Monitor screen without a tool tip indicating why.
In this picture, the Prepare screen with the question mark shown:
In this picture, the Monitor screen with the question mark still shown:
The question mark went away after starting a print.
In this picture, the Monitor screen with a print underway and the question mark no longer shown:
Here is the terminal code that was cut off as it was dynamically generating new lines after the print started:
I think a hover state (over the question mark) indicating to the user why the question mark is there would be helpful.