Try looking at the switch, is current getting to it? and is the current getting from it to the motor?
The switches get dirty contacts, you can pull them apart and clean the contacts.
If that all checks out, then have a look at the gearbox on the motor, the gearboxes strip out the gears.
You’ll be up for a new motor, if it’s buggered
Let us know how you go with that lot, and if the problem still exists we can guide you further.
"Keep calm, relax, focus on the problem & PULL THE BLOODY TRIGGER"