This error is usually preceded by a line that looks like this:
< 2:41:10 PM: : Extruder switched off. MINTEMP triggered !
Is that what you're seeing?
Mintemp is designed to shut the machine off if the thermistor becomes disconnected to keep it from heating out of control. Once mintemp is triggered, you will not be able to heat the nozzle because it is not safe to power the heater when the thermistor is not functioning properly.
To fix this error, you need to make sure that your thermistor is connected properly. On the X1, the extruder thermistor connection is labeled E-TRM. On the X3, the T0 thermistor connection is labeled E0 and the T1 thermistor connector is labeled E2, and both will need to be connected for a Duo to avoid this error.