This is basically as simple as the title suggests. From last Friday, a site to site VPN connection ceased working for no visible reason. There have been no changes to Azure config, or local network. Using our local sonicwall, we can see traffic attempting the Ike negotiation, but then remote party timeout.
Azure says that the VPN gateway is not publicly visible, but it is, from various places I have tested, only Azure is at fault. I have deleted and recreated the local gateway and connection within our Azure tenancy, and updated the preshared ike passwhrase locally, in essence to try to recreate the connection from scratch, but this is not working.