VEVOR Professional Ultrasonic Cleaner, 30 L Ultrasonic Jewelry Cleaner with Digital Timer & Heater, Stainless Steel Industrial Sonic Cleaner 40kHz for Glasses, Watches, Rings, Small Parts
If the switch on the back of the machine doesn't light up, it might be because the switch fuse is burnt out. You'll need to replace the switch fuse. See the link for the replacement method: https://youtu.be/XG-5VOMCOLw