To turn off this notification see
Action Center - Change Message Settings
This is a Windows bug as richc46 pointed out. If for any reason Norton can't function properly, it will display a red circle with a white 'x' in the system tray as opposed to the usual green circle with a white tick.
If you would prefer to have Windows recognise Norton, a uninstall and reinstall will often do it. (Usually takes 2 minutes minus reboots.)
There is no 'best' anti-virus as richc46 proclaims. Norton provides excellent protection (none are perfect) and I suggest changing only if Norton starts giving you grief or you don't get Norton for free (from your ISP, for example) and would rather not having to pay subscriptions to Norton.
What's the Best Anti-virus?