In /etc/modules.conf is sip loaded?

load => chan_sip.so ;                           Session Initiation Protocol (SIP)

Check against what I am using below, another issue I have run into is sometimes after boot I have to run

asterisk -rx "sip reload" to get it to connect/work... 

Hope this helps...

SIP.conf:

; SIP Configuration example for Asterisk

;

[general]

context = default

                                ; Default context for incoming calls

allowoverlap = no               ; Disable overlap dialing support. (Default is yes)

bindport = 5060                 ; UDP Port to bind to (SIP standard port is 5060)

bindaddr = 0.0.0.0              ; IP address to bind to (0.0.0.0 binds to all)

srvlookup = yes                 ; Enable DNS SRV lookups on outbound calls

                                ; Note: Asterisk only uses the first host

                                ; in SRV records

                                ; Disabling DNS SRV lookups disables the

                                ; ability to place SIP calls based on domain

                                ; names to some other SIP users on the Internet

dtmfmode = rfc2833

context=from-callcentric

srvlookup=yes

register => 1777:YOURPASSWORDHERE@callcentric.com

session-timers=refuse

[callcentric]

type=peer

context=from-callcentric

host=callcentric.com

fromdomain=callcentric.com

username=1777........

fromuser=1777........

secret=YOURPASSWORDHERE

insecure=port,invite

canreinvite=no

disallow=all

allow=ulaw

[100] ;this is your extension # at call centric. usually 100-150

context=to-callcentric

type=friend

defaultuser=1777.......

secret=YOURPASSWORDHERE

host=dynamic

Extensions.conf:

[to-callcentric]

exten => _X.,1,Dial(SIP/${EXTEN}@callcentric)

RPT.conf:

6=autopatchup,context=to-callcentric,noct=1,farenddisconnect=1,dialtime=20000