I have had non stop issues with the notifications, or lack there of. All of my notifications are turned on for chats but they will, almost everyday, just stop coming through to me on my phone. Once I realize that they've stopped, usually because an email has come through to tell me of unread chats, I have to go into the settings and turn them off and then back on again. I have done everything that the support pages suggest and it's still happening months later.