asterisk users - Jan 2005 - Got SIP response 481 "Call Leg/Transaction Does Not Exist" back from 24.172.221.22

I have a PCPHONELINE SIS phone set it up to asterisk

Registered SIP '205' at 24.172.221.22 port 2770 expires 120 (Port
changes
every time)
Got SIP response 481 "Call Leg/Transaction Does Not Exist" back from
24.172.221.22(24.172.221.22 is my phones IP)

Anyone have an idea what the problem is?

Jeff