This may sound like a stupid question,…but quite often the Comodo logo in the tray will have a “No” sign (red circle with a line through it) in the lower right corner. What does that mean,…and should I be worried? Thanks!
Welcome. 
That sign normally tells you CIS is not functioning correctly, but it’s a known bug that should be fixed in the future.
Just to make sure, go to Miscellaneous > Diagnostics and run it. If it reports everything is okay, then this sign on the tray icon is most likely the bug.
Thanks,…guess it wasn’t a stupid question after all!
Cheers! 
No, it wasn’t stupid. It was smart of you to ask.