I really hate that badspot added UPnP, its really unreliable and it lets literally anyone host a server, which is far more bad than it is good
when port forwarding was a requirement to host a server, it restricted the feature to people with at least a shred of intelligence, and since that's no longer true the server list is saturated with really poor servers
but as aforementioned, UPnP is really unreliable, immediately after you start up your server you should check your console to make sure it isn't erroring out when trying to initialize UPnP, and if it does you should close the game and try again