There's still no fix for the 9999 ping bug. I use the ping plugin on the main project for it, though, and broadcast the hosts IP as a session variable. The problem is Epic hasn't implemented pings for listen server sessions.
As far as the hosting and seeing sessions goes, I've had problems with LAN and WiFi. I'm sure it has something to do with network configuration. (Possibly a security setting about broadcasting packets over a WiFi access point)
If your test was over the internet, it could also be firewall rules causing the issue or Steam region lock. Since this uses Steam Test APPID's, sometimes I've had issues with Steam. If you have your own APPID, then that issue should go away. (If it's related to region locking)
Those are the three issues I've seen.
Was your multiplayer session broadcast test over LAN with WiFi? Or over the internet?