Whenever I log on, I only see maybe 30-40 people in the chat rooms at any given time, but if I am searching for a particular file, usernames come up that are nowhere in chat...where are these people and how do I know who's really online? Are the rest in private chat rooms?

you dont have to be in any channels to use fopnu.

I know, is there any way to find out who's online in Fopnu? Also, having a real tough time connecting to the chat rooms...never used to...do I need to make some sort of adjustment?

as stated channels are optional. you can have 1000 online users and only 10 in a chatroom. Some might be in private chatrooms, but they also can be in no rooms

if you have a friend, you can add them to your contact list and you will see from that whether or not they are online at any given time.

there is no way to know all the users online.