That's because TCAdmins default firewall rules aren't really fantastic.
TCAdmin will allow the application to use any port (pointless really) since Minecraft is a Java process you need to allow the Java application inbound connections.
TL;DR
Use this script.
Add it in Games > Minecraft > Custom Scripts
-- Before Created --
netsh advfirewall firewall add rule name="ID:%ThisService_ServiceId% USER:%ThisUser_UserName% GAME:%ThisGame_ShortName% IP/PORT:%ThisService_ConnectionInfo% TCP" dir=in action=allow program="C:\TCAFiles\Users\%ThisUser_UserName%\%ThisService_ServiceId%\Java\jre7\bin\java.exe" localport="%ThisService_GamePort%,%ThisService_RConPort%,%ThisService_CustomPort1%,%ThisService_CustomPort2%,%ThisService_CustomPort3%,%ThisService_CustomPort4%,%ThisService_CustomPort5%" protocol=TCP
-- Before Deleted --
netsh advfirewall firewall delete rule name="ID:%ThisService_ServiceId% USER:%ThisUser_UserName% GAME:%ThisGame_ShortName% IP/PORT:%ThisService_ConnectionInfo% TCP"