Diagnosis
E1 is a temperature sensor fault. The unit has a sensor that reads the room temp, and if that sensor's readings are out of whack or the wiring is bad, it throws this code to protect itself.
How to Fix It
Unplug the unit from the wall for a full 5 minutes. This is a hard reset that clears the error memory. After 5 minutes, plug it back in. If the room is at a normal temperature (above 41°F), it should start up normally and the E1 should be gone.
If That Didn't Work
The issue might be more permanent. With the unit unplugged, open the front grille (it usually snaps off) and gently check the wires connected to the main control board and the sensor. Look for any that are loose, disconnected, or chewed through. If you see obvious damage, that's your culprit.
Heads Up
Don't try to run it with the E1 code showing. It won't dehumidify correctly and could cause other issues. If the reset doesn't fix it, you're likely looking at a repair call for the sensor or main board.