Problem with inbound CallCentric calls

I am fairly new at asterisk first of all. I have an inbound DID with CallCentric. When I attempt to call this number, it fails with the following in the console:

[May 27 04:54:04] NOTICE[31510]: chan_sip.c:14033 handle_request_invite: Call from ‘’ to extension ‘17772744835’ rejected because extension not found.
[May 27 04:54:23] NOTICE[31510]: chan_sip.c:14033 handle_request_invite: Call from ‘17772744835’ to extension ‘17772744835’ rejected because extension not found.

Working with CallCentric support, I completely wiped out my asterisk config and put only what their support page suggested. I also upgraded my asterisk to 1.4.20.1 and still have the same results. I would greatly appreciate any suggestions. I’ve spent all weekend working on this with support and still no success. My sip.conf and extensions.conf are fairly short now so I’ll post them below. Thanks in advance.

sip.conf

[general]
dtmfmode = rfc2833
context=from-callcentric
srvlookup=yes
register => 17772744835:mypass123@callcentric.com/17772744835

[callcentric]
type=friend
context=from-callcentric
host=callcentric.com
username=17772744835
secret=mypass123
fromuser=17772744835
fromdomain=callcentric.com
insecure=port,invite

[123]
context=to-callcentric
type=friend
username=123
secret=PHONESECRET
host=dynamic

[1000]
context=to-callcentric
type=friend
username=1000
host=dynamic

extensions.conf

[general]
autofallthrough=yes

[globals]

[from-callcentric]
;exten => s,1,Dial(SIP/123)
exten => s,1,Answer()
exten => s,n,Playback(hello-world)
exten => s,n,Hangup()