Sometime my friends show up as active now without green light below their names - what does it mean? Is it say that the person is chatting or just pop up into the Messenger for very short time?
'Active Now' with green dot means person is online and visible to their Messenger contacts.
Refresh the Messenger, if you still see 'Active Now' without green dot that means they might have their chat turned off or you have turned off your chat.
Learn more about messages on Facebook.
For Messenger app or messenger.com, visit the Messenger Help Center.
Go to messenger settings in notifications and sounds there is a setting "light" if it's slid to the right and the circle is blue it's on. Just click it to run it off.