Sky (UK Broadband) and Sipgate

[Owain]

Help please. Having problems with a Yealink T28 and Sipgate (and A&A) accounts after changing to Sky and the new Sky router. Previously worked fine for years with Talktalk and Plusnet but I've made that many changes to the phone's settings sinc Sky started, fiddling it's like fumbling in the dark with a car engine and realising I've dismantled it to meccano level.

I've updated the phone's firmware to latest version and put my details in exactly as at
https://basichelp.sipgate.co.uk/hc/en-gb/articles/204237021-Yealink including local SIP port to 49860 and setting NAT to STUN.

I can't reach the phone on http:// IPv4 address but can on http:// [IPv6] address. The phone is set to use both IP v4 and IP v6 networking. The phone says it has an IP v4 address but isn't currently showing on "Attached devices" to the hub with IP v4, but is with IP v6.

STUN server is the sipgate one. From the laptop:

Pinging stun.sipgate.net [217.10.68.152] with 32 byte
Reply from 217.10.68.152: bytes=32 time=36ms TTL=56
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss)

From the router diagnostics DNS test stun.sipgate.net resolves the above IP v4 address but does not resolve IP v6.

I've tried changing the phone to IP v4 networking only and rebooted it, but no success either.

I've opened an IP v6 firewall for incoming UDP to the phone.

I know Sky routers have issues with ALG and Sky help don't have a script to cope with it.  (I thought IP v6 was supposed to solve lots of these problems)

The phone sends ages "sending provision requests" then tries to register with its line key(s) flashing very festively but always Register Fails.

Any suggestions for a methodical approach? If I can get one account working then I can start incrementing port numbers etc for the rest (and my aging mother who is in hospital hundreds of miles away will be able to phone me for christmas)