We are running two SWAT 4 servers:

http://www.gametracker.com/server_info/80.57.134.98:10280/
http://www.gametracker.com/server_info/80.57.134.98:10480/

For both servers, GT reports status: dead

However, both servers are online and seem to respond to incoming queries on the WAN IP on their query port (10281 and 10481 respectively) just fine.

I tried querying the server on the assigned query port using the standard \status\ gamespy query and the server responds accordingly.

Here's an example response:
\hostname\[c=ffff00]HOUSE OF PAiN\numplayers\7\maxplayers\10\gametype\Barricaded Suspects\gamevariant\SWAT 4\mapname\Food Wall Restaurant\hostport\10480\password\0\gamever\1.0\player_0\sinaCRO\player_1\booga\player_2\TrY\player_3\[C=FB02D2]jaffa\player_4\|SoH|Cold\player_5\MacaN\player_6\|SKY|ThePeaceMaker\score_0\2\score_1\1\score_2\0\score_3\0\score_4\5\score_5\12\score_6\6\ping_0\67\ping_1\177\ping_2\118\ping_3\156\ping_4\105\ping_5\86\ping_6\56\final\\queryid\1.1

Any ideas why GT thinks they are dead?

EDIT: the forum seems to cut off the response text, I pasted it in full here: http://pastebin.com/3MYmEhms

Hello,

Your server does not seem to be responding to the stats query to the GT scanner. When I tried scanning it on HLSW, it also did not scan but I did notice packets with the "HOUSE OF PAIN" text. I would suspect that your server is either not completing the stats request or is not sending what the scanner is expecting for the gamespy2 protocol.

You may want to ensure the query port is open in your firewall (UDP). If you run any mods, especially if you have changed anything recently, you may want to take them off temporarily. Otherwise, you could try to reinstall the server to see if it works under a vanilla installation.