Earlier, Facebook used to show online members at the top in group chat box but recently I have noticed that it no longer does.
Chat option is still available but the list of online members has just disappeared.
What might be the problem?
Is this bug from Facebook? OR is this a new change from Facebook?
Or do I need to change the Group's Setting?
It was (and still) due to the changes Facebook made in their group structure, that since then kept changing.
The only way now to see a list of online friends is via the chat windows - there's no option to see which members from a group are online.
Sometimes you might see an online (green) indication dot near the profile of a user in a group feed, but that's all.
I think it was a way of Facebook to make people feel they have more privacy and that strangers can't see their online status in a group even if they share a group.