@Phaedrux Yes, that was exactly what was happening

Solved, my firmware needed an update

My Duet 2 Wifi displays temperatures of 2000c for all thermistors, consistent with an open circuit.
I have tried several thermistors in case the one I was using was bad.
My Config.g includes the following:
"M308 S1 P"e0temp" Y"thermistor" T100000 B4138 ; configure sensor 1 as thermistor on pin e0temp"
When I connect a 220k resistor instead of a thermistor, the temperature reading does not change.
Any idea what could be causing this?

Thanks for your reply. Unfortunately, my duet does not even appear as "Bossa Port," which I believe would be the case if my firmware was erased as described in fallback procedure 3.

Hi, I have had my Duet WiFi for less than a month. Recently, I have been unable to connect to it in any way. The green LED also does not turn on. No endstops were ever connected. The only things ever plugged into the board were motors, a hotend heater, a thermistor, and an always-on fan.
Thank you in advance for your help.