All wireless connection devices have internal NAT firewalls which block ports. So wherever this device is ... is most likely the culprit. Whether that is your receiver or the sender is the question.

I presume this is a radio service right? You receive the signal directly from your isp? If directly from your isp then the earlier suggestion the isp is to blame might be the issue. So ask them to open the port LW uses. But try Sleepless's suggestion anyway.