Answer 1

Hey - Sorry for the delayed reply. There is a Repairs Sheet here http://www.manualslib.com/manual/547914/Ryobi-Js651l.html specific for the Ryobi JS651L that shoulc be of much help. Comment below for any further needed  help on this.

Comments

According to the repair sheet on page 4, the fuse is located on the circuit board. Did you manage to access the board, refer on the diagram on page 4 from the link by Kervin above.
Check if the gear assembly is not jammed.
The brushes may be dirty.
Trigger switch may be broken, try bypassing the switch to see if it won`t run, if running then replace the switch.
Another possible course can be the motor, it may need to be rebuild.

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