Hi Shane,
Your SIP port is either not working..or you need to get that activated from your Bandwidth provider…If you have PTCL’s DXX than 5060 port is enabled…with other ISPs its always an issue..
Are you using IP-PBX? if that’s the case..than check the settings after getting confirmations from your BW provider about the said port.
Feel free to contact me at bilal@callplanet.net for any assistance.