JC Try your sip2sip account from a sip phone such as xlite and see if it is working!
Also as per sip2sip if your router has SIP ALG, Disable SIP ALG in some cases that can cause sip2sip not register. Also try nat=no.
sip2sip service is running fine I have 5 of my remote extensions registered with them and the are all working fine including my PBXinaFLASH.
Definitely a puzzle
I downloaded Blink and set that up on my Ubuntu laptop behind the same router. Works fine as far as the incoming and echo tests are concerned. The only differences I see between the Blink setup and Asterisk/PIAF is that Blink uses an Outbound Proxy setting.
Interestingly I also tried their suggested software SIP Communicator and that would not connect either with the following error... which means nothing to me: We failed to create your account due to the following error: "Index: 0, Size: 0"
I added what I believe to be the equivalent to the PEER Details, "outboundproxy=proxy.sipthor.net", but unfortunately it changed nothing, so I dumped that addition. I also tried your suggestion of "nat=no", but no change there either.
I have used both host= sip2sip.info and proxy.sipthor.net. (as well as proxy.sipthor.net in the reg string). The only thing I can think of is that my eyes are shot all to h*** and I'm missing something very obvious, which is why I posted my setup last night... lucky for that in one respect, the codc error was caught.
Oh well, something will strike someone and the lightbulb will light... maybe even here! In the meantime I will hold off before contacting sip2sip for suggestions... I hate to bug them unnecessarily considering it's a free service.
Ultimately, though, what I suspect is that my dns server is not returning the proper SRV record since I have sip2sip.info in the registration string, but tcpdump is showing the reply from redirect.dns-hosting.info... That ain't right.
I'm gonna play with that piece next. That may be the lightbulb I've been waiting for!
Thanks again.
JC