I may be repeating things you’ve already tried, but here’s what to try.
Confirm your iPhones are running IOS 10 or higher.
Confirm you are using the goTenna Mesh app (purple logo) and not the goTenna Pro app (logo is black).
Confirm that the apps on each phone show neither is paired.
Turn on one of your phones and complete setting up one of the GTM device via your app. The other device should be off and its phone should be off, too,.
After the first iPhone is paired, try sending a Shout.
Turn off your just paired first set of devices.
Try pairing the other pair, carefully observing the GTM’s install; as with the first,.
Worth checking> Does the location on your phone match your physical location?
Is this the address you’ve been using to try to contact Support? email@example.com
More here: https://support.gotennamesh.com/hc/en-us/articles/360021110291-goTenna-Mesh-Resolutions
The one thing that seems odd is that you say they’re running firmware version 1.1.12. which I thought was only applied in one of the SDK versions.
Finally, goTenna is located in the center of the worst of the COVID-19 pandemic. I presume everyone’s working at home, but would think that someone would be available to help. If not, then some extended patience is in order. They should’ve answered before now, I’d think, but right now things could be a little up in the air.