Do you mean that water is running thru the machine and it is not making ice, or that the compressor is not running?
Is the machine in ice mode or clean mode?
Is water being pumped over the ice plate?
If so, is any dropping into the ice bin or going down the drain?
Is the machine water, air cooled or remote condenser?
Have you checked the high head safety? If it is water cooled and ran without water this will trip. It will also trip if the cooling fan on a air cooled unit stops or gets a obstructed coil..Last, check the harvest light to make sure it is open (dark) or minor flashes from water. also the harvest cover has a magnetic switch to tell it harvest is over and ready to make ice. Magnet is in the edge of the cover and operates a reed switch on the right side of the ice plate.
    In all my years of working on these, I’ve never had a bad board. Can’t say the same for Scotsman.
If you can answer the questions we can probably help you.
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I forgot that this was a under-counter. Most applies, but check the drain pan as they break and drop on one side and leak.