If the thick frost covered most or all of the evap it is not defrosting, probably due to an open defrost circuit. You may have an open defrost thermostat or thermodisc that is not allowing it to defrost. Less likely is an open defrost heater. While it is iced up you can test the whole defrost system at the control board, I think the plugs are marked. It'll be the thicker wires on the board.

For the short term if you let it defrost fully in open air it will buy you a week or 2 to source the part. Empty the machine, unplug it and either let time do it or use a heat gun, steamer, or even small space heater to speed it up. Once that frost is gone it will begin to cool again until it builds up enough to block airflow.

If you want further guidance on testing I'll pull wiring diagram on Monday if I can and get you wire colors to test. Neither repair is hard. I'd bet on thermostat. If you defrost it and it is bulged out or looks odd that is a sign of failure.