We have been struggling to get a VPN between our Azure environment and Untangle. After alot of digging around and piecing together bits of information from posts, we now have a working solution. Untangle's IPSec appliance uses IKEv1. You can manually change the version to IKEv2 in the config files but it is not persistent. On Azure, there are 2 different routing options you can choose. What they don't say is that dynamic uses IKEv2 and static uses IKEv1. After changing the Azure VPN to use static routing, everything has been working and stable. Hope this can help some of you guys out because it was a struggle to get this figured out.