The 9999 ping is because Epic only has it working for dedicated servers. Also, the ping plugin has been having issues on some setups and that's why it throws a "-" or a "?". Sometimes after a while the actual ping will show up. I think they are firewall issues. I know some Wireless Access Points will block the ping traffic along with some local and network firewalls. The ping plugin is simple and doesn't have a way to open ports automatically. Using it on a VPS linux machine to host, I haven't had issues. But I haven't used wireshark or anything to try and discover why some Windows machines are having issues. The ping plugin has gone out of support with the original developer. They are using a much older version of UE4 with their project. Personally, I've been waiting for Epic's new online framework to investigate further. If you figure out how to get it to work on your setup, tell us what was blocking the ping and what you did to get it to work?