Engineer here that works on the original devices noted. To add a little more data:
The devices are in a couple of groups that are ~150 miles apart, one group’s devices are all within 100 feet of each other, another group is half a mile from the next device, and then there’s two more that are 50-100 miles from any other device. I think that rules out a tower problem (these are all LTE devices) at least.
The devices (at least the ones I can physically access), seem to think everything is just fine. They boot, connect, go in to a “breathing” (cloud connection?) status and pretend to post data before going back to sleep. I have a couple outside of cases that I get diagnostic data over serial, they just go through their process with no errors. Weird right?
Might be important there too: these being remote, solar powered setups they are asleep most of the time. If their batteries are particularly healthy they will stay awake for a few minutes to capture a GPS signal while not connected before connecting, posting data again, and going back to sleep. But otherwise asleep for ~29.5 minutes out of every 30.
All of them stopped registering with particle at about 2-3:00pm EST on 5/2. One (of ~20) came back online by itself today, and there are a few others that I have de-powered and reset or reloaded the firmware on that are back online. Most of the devices are in hermetically sealed cases and I wont have the physical access to unplug or reload. Hopefully the particle team can (re-provision?) them so we don’t have to have to go on a road trip and break the seals on our devices!