If you are using port 30121, make sure that port has been port forwarded correctly. On the top of the cfg file, you will see

endpoint_add_tcp "0.0.0.0:30120"
endpoint_add_udp "0.0.0.0:30120"

Simply alter that to

endpoint_add_tcp "0.0.0.0:30121"
endpoint_add_udp "0.0.0.0:30121"