There are two temperature setting knobs (thermostats); one for electric and one for gas. Did you set the electric knob to at least five? Your heating element could be bad; it is easy to replace.
In the center photo I posted; just above my hand there are wires inside a rust colored sheath. The original element had ceramic beads over the wires to protect them from the heat. These go to the heating element which is behind the metal shield that covers the burner, the one with the name plate on it in the photo. Some fiberglass insulation is covering the pipe (or well) where the element is located. Just follow the wires and you will find the element.
But before you go to the trouble of removing the shield, check to make sure you have 120 volt AC power to the heating element terminals, which are just above where my hand is in the center picture; just follow the wires, they are connected with stab on connectors.. Set the electric thermostat all the way to max, make sure the refer is plugged into the outlet and make sure the outlet has power.
If you have power to the heating element terminals. Check the piping that comes out above the shield previously mentioned. If it is not warm to the touch, the heating element is bad. It is only 150 watts, so give it a couple of hours with confirmed power on before you check the piping.
This refer does not use 12 volt
power; it only runs in the electric or gas mode. You need 120 volt AC power for it to work in the electric mode.
My refer was out when I replaced the element, the PO said it didn't work and had removed it, I threw it in my truck and brought it home with the trailer. Turns out that all that was wrong with it was the heating element was bad and it was missing the thermo couple for the gas mode. I installed a new element and a thermocouple. It has been working fine.
I think you can get to the element without removing the refer, but I'm not absolutely sure. If you can get the shield off you can replace it in place.