Circuit to power socket may have tripped breaker
Socket itself may be defective
Fuse in plug (if you have a fused plug) may be blown
Conductor in plug may have worked loose
Power cord may have severed conductor (take care when checking)
Connector at lawnmower end may be defective
Power switch on mower may be defective
Internal wiring in mower may be defective (probably not though)
Motor and or brushes may be defective.
Check the easiest things first...
Try not to be too frustrated - in the overall scheme of things a non-working lawnmower hardly counts - it's just part of everyday life - stay cool.
Peccavi
April 2009