I know this is an issue for a lot of people, but none of the recommended fixes do anything for me. Whenever I click on "friend and chat" in the bottom right, or if I click "unread chat message" in my notifications, nothing happens. No pop up, no friends list, no messages, nothing. It's been like this for well over a year, probably at least two. It's not a huge problem, but it is really annoying.
No issues when in-game with the steam overlay, just within the steam app itself.