Cisco SPA303 sending 486 BUSY when not busy

Here is the problem, I have recently added an office and I’m trying to get the phones they have SPA303’s to add an extension to our freepbx while still talking to vonage. The phone shows that the ext is registered, the pbx says it’s registered but when you make a call to that phone it says fast busy and if you look at the debug you get 486 Busy message. I can call the phone on the vonage ext so I know that the phone is not on dnd. Any help is appreciated. Other extensions that display as registered are not having this problem.

Important network info:
Phone 2501 is behind a sonicwall that is performing a lan to lan vpn where is translated to

I’m running: FreePBX, and Asterisk Version: 13.12.2

Phone Status for FreePBX Ext:
Ext 3 Status
Registration State: Registered
Last Registration At: 12/16/2016 09:36:07
Next Registration In: 211 s
Message Waiting: No
Mapped SIP Port: 5060

Info from SIP Peers on the FreePBX showing only relevant ext.
Name/username Host Dyn Forcerport Comedia ACL Port Status Description
1899/1899 D Yes Yes A 5060 OK (27 ms)
2501/2501 D Yes Yes A 5060 OK (39 ms)

Debug from asterisk:
<— SIP read from UDP: —>
SIP/2.0 486 Busy Here
To: sip:[email protected]:5060;tag=147f6dce74d8fbdai2
From: “netpanda” sip:[email protected];tag=as1722d9d4
Call-ID: [email protected]:5060
CSeq: 102 INVITE
Via: SIP/2.0/UDP;branch=z9hG4bK790c1117;rport=5060
Server: Cisco/SPA303-7.5.5
Content-Length: 0

Don’t see any FreePBX issue here.
Make sure that on SPA you have the desired Ext X assigned to a Line key.
P.S. please try to post readable logs.

That was it, for everyone who has this problem in the future.

Log into the SPA303’s phone interface go to admin and advanced.
Click Phone, then make sure the extension you configured is attached to a line key.

Thank you Andrew!