Trying to set up remote extension

I’m running FreePBX and I’ve set up a remote extension phone (11) that is registered to my PBX but when I dial the number from an internal extension (13) it rings for a fraction of a second and then goes to engaged tone. I’ve set up port forwarding correctly but there are so many different settings in freepbx I don’t know where to start to troubleshoot this. I did a debug while dialling and i saw ‘SIP/2.0 404 Not Found’ but I don’t know what this actually means or where the problem is. Here is the debug:
.debug text file I’ve been trawling google for ages but can’t find any straightforward guide that shows how to set up a remote extension. I have however found dead links, out-of-date tutorials and many failed requests about this subject that lead nowhere. thanks for any help.

thanks for your response but in providing that link are you saying there isn’t enough verbosity in my debug? is it the wrong type of debug? is it in the wrong place? some clarification would be appreciated.

Yes, the context of the call flow would help.

The usual cause of a 404 returned by an external extension is NAT association timeouts. If you have e.g. extensions 13 and 14 registered behind the same NAT using the same source port numbers and they get confused by the router, the INVITE to 13 could be sent to 14. The device at 14 would not recognize the called number 13 so would return a 404.

Please confirm that you have only one extension behind the Sky connection NAT and that it has only one line configured.

<--- SIP read from UDP: --->
SIP/2.0 404 Not Found
Via: SIP/2.0/UDP;branch=z9hG4bK162fc794;rport
From: "13" <sip:[email protected]>;tag=as572d938e
To: <sip:[email protected]:5061;transport=udp>
Call-ID: [email protected]:5060
Date: Sat, 28 Nov 2020 22:32:10 GMT
CSeq: 102 INVITE
Content-Length: 0

Where did come from? Is this the private address of the extension? The Via header in a response should be a copy of that in the request, possibly with added tags. Also, there is no User-Agent or Server header present.

I am guessing that either this is a really ancient device, more than 15 years old, or the reply was dummied up by a SIP ALG somewhere.

It it’s old, try shutting the device down and registering something else (softphone, SIP app, etc.) in its place.

Please post details about the router/firewalls on both the Sky and Plus connections.

The info was fine, though we would prefer that you paste it at and post the link here. This makes it less likely that removal of the info would prevent a future reader from following the thread.

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