Just to make a note of it here. We went out yesterday to swap in a SD card, since Shane wanted to look at its data, and since we wanted to make sure it was working. Turns out it's been taking data but the time is completely wrong (Jan 2000), since apparently it's not getting time from the network. We went back out to replace the one that doesn't connect to the internet (numbered 2) with the one that does connect to the internet, but doesn't recognize its SD card (numbered 3). The new PurpleAir is collecting data, and it's getting to the PurpleAir map, so at least we'll be able to download it from there.
Of course, back at the base, the bad one is connecting to dsm wifi just fine...