Ever since the new update, every time me or my friends message each other on the friends chat, it disappears..

Ever since the new update, every time me or my friends message each other on the friends chat, it disappears for me when I click off of the chat. Which is really bad for when 2 or more of my friends are online at the same time since it doesnt give me a notification for when they message me so long as I'm on a different person's chat. So I can only talk to one person. I can only see the past messages from before the update. I'd really REALLY appreciate if someone could help me fix this.