This may be because the digital overload protection has been triggered. Set the machine to “Off” and then start the machine up again. If the machine is subjected to heavy loads, one way to deal with this is to increase the speed slightly. The machine can also switch itself off if the thermal cutout is triggered by the motor getting too hot. The machine then needs to rest a while before it can be used again. If you have been running large volumes in it, with quite a lot of resistance, you need to switch the machine off and wait for a few minutes.