Ice machines are tricky. With different operating components, there is a lot that can go wrong with them. A combination of sensors, solenoid inlet and purge valves, thickness and thermistor probes, float switches, refrigeration circuit, all work together for proper operation of the unit. These items are going to vary depending on the brand and type of machine you have. So servicing them can be deceiving at times.
Maintenance is key here, most ice machine issues stem from not being maintained.
In a nutshell, the ice machine is a low-temp refrigeration circuit with sensors monitoring binary/analog inputs, then sent to the control board(s), and then sent out as binary outputs as to what it should be doing.
After the unit reaches a certain number of faults, the machine will cut off unit until the issue is resolved and reset. When you look on the inside panel of the machine you will see a schematic, a series of operation, and the fault codes (if applicable). This will give you a place to start and possibly determine what is wrong with the machine.