I have a Uniworld UPM-20E commercial mixer. I bought used from another baker and it was working when I bought it.
Electric devices get damaged sometimes by internal corrosion even if you don't use them. If you have the technical knowledge, take apart the control board or control panel, probably you've got some contact problem. you might be able repair it by cleaning or maybe you might need some part to replace.
If you don't have real knowledge repairing this kind of an appliance, my best advice: take it to a repair service.
Some time ago I tried to do a similar job with my home mixer and had to take pieces in a shoebox to a repair service ; I took it apart, cleaned contacts bur couldn't assemble it againbecause after taking it apat, couldn't assemble it again
on Aug 21, 2015