Chances are it's not your element due to the type it is.
The Defrost thermostat is part number AP175103
Defrost timer Part AP98191 (since your frig has this type of timer. located on the back near the compressor) Try this first Leave the machine plugged in and turn the little red "knob" a little at a time until your frig kicks off. then wait and listen for popping ice, maybe some sizzling if so then is' defrosting and should kick back on in about 30 minutes. If not then defrost your frig manually as I stated before and we will figure out which part is out.
toni_ post your model number please