Hey, Griff; welcome!
I used to have a perspective, when I worked on customers' equipment. 'It used to work, now it doesn't; what's changed.'
All of the possible (probable) reasons are electrical...the brushes, faulty switch, faulty electronics, or faulty plug/power cord.
The brushes would seem to be the easiest to remedy, and what's the downside to replacing them in any case?
After that, play with the obvious stuff; go to a wall plug that you know works and isn't the one you normally use, for starters.
Then check out the cord and plug connections, carefully. Now you're closing in on the switch and electronics.
The motor is a last resort...you probably would have smelled burning insulation.