Thank you for your help denman. When the block of ice thawed the problem was apparent - the heating element was unplugged. How this happened when I have never had the back panel off is a mystery. I ran continuity checks on heater and thermostat (before it thawed) and it looked OK. I put some ice around the element, plugged it in and went to bed. Ice was melted in the morning so I think I'm good to go. I'm printing the force defrost instructions you referenced and taping them to the back for future reference.

Typical problem - freezer not defrosting and fridge gets warm. Took off back cover of freezer and solid ice. All fans and compressors running. How can I force the defrost cycle with electronic control board. I figure if I force defrost and it works, it must be the control board. If not I'll have to troubleshoot thermostat, heater, etc. I've searched all over and can't seem to find the procedure for my model. My wife is having a party this weekend and if I can't get it fixed pronto she is going appliance shopping - ouch!