Can't make outgoing calls on Grandstream phones w/ FreePBX

Starting yesterday afternoon, I have 2 sites that have grand stream phones connected to cloud based Free PBX and outbound or “internal” extension calls are unable to be made…I have attached a trace showing me making an inbound call and answering. I then try to make an outbound (both calls to 701.212.5263) and it fails…I then make an internal call using Bria soft phone “internally” from extension 15 to 11, and it works inbound on 11 (grand stream phone), but I can’t call outbound on the grand stream phone.

It appears this is an issue related to grand stream hardware, as the Bria soft phone has no issues.

Here’s a link to the PCAP

You have to turn off the grandstream-pbx sip header for each registered account

<!-- Disable Grandstream-PBX-Header Account 1-->

interestingly enough, all it took to fix this was within GDMS (grand streams provisioning service) / SIP Server toggle the NAT transversal to Auto…

The question as to why this randomly happened on two of the dozen or so identical systems I have in production will remain a mystery…