T1 with an external firewall

I have a T1 line and am trying to hook up a external firewall and am haveing trouble getting threw it. The T1 router is a niva 200 and the fire wall is a dlink 701. I think that might be the problem but I’m not sure. Coming out of the T1 is an 10BASE T port that goe’s straight to the 10/100 hub and all the systems work fine that way but when I put the firewall in between the T1 router and the hub nothing works. I can see the firewall but thats it.