This is what i am doing… and what is (not) happening…
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I create an application that has two buttons… JOIN ROOM and CREATE ROOM… and an indication if OnRoomListUpdate() is ever called…
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i run two identical copies of the application… with one of the running applications i CREATE a room (with RoomOptions: IsVisible = true and Max Player = 4)… but the other running application NEVER fires OnRoomListUpdate()…
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and yet… with this other running application if i JOIN ROOM it joins the room the first one CREATED just fine …
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note that since it is the same app it obviously has the same AppID… and i made sure the Room created has IsVisible set to true…
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also… the OnRoomListUpdate() callback is in the same class as callbacks like the OnJoinRoom()… which are called just fine…
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i am not entirely sure what constitutes a ‘lobby’… i thought as long as i can CREATE a Room with one app and JOIN that Room with another they must be in the same ‘lobby’… but i never create a ‘lobby’… even though i have seen discussions where people talk about different ‘lobby’ TYPES…
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anyway… how do i get OnRoomListUpdate() to work/fire?
RESOLVED: i had to add JoinLobby() to the code… now it works! 
Where did you call JoinLobby()?
Yeaa I also encounter this problem, where did you call the PhotonNetwork.JoinLobby()?
The PUN Basics Tutorial covers using the lobby, listing rooms, etc.
There are plenty of docs for PUN, so if anything doesn’t work the way you think it does, check the docs next. It should get you unblocked in a shorter time.
Also, the Asteroids Demo in the package has a lobby, too.