sometimes the culprit behind a fryer not working is a broken part. Thankfully these can be replaced by a service technician. A common part that gets replaced on commercial fryers though is the thermostat. Whether it's old or was faulty, these deep fryer thermostat replacement instructions will help to get a new one installed.
For more technician training resources, visit the techtown Knowledge Base: https://www.techtownforum.com/knowledge-base/
Shop real OEM fryer parts to streamline the repair process: https://www.partstown.com/fryer-parts