Hi from Essex In the UK
I would look at the battery, now be carful !!!
I have used jumper leads to try and start a mower with no luck and as the engine did not turn over I stated to look at all the electrics
But the jump leads were to long and losing to much power thought them
So I got a jump pack hooked this up and what do you know it started first time, this is what I mean by be carful don't thing all is fine with the battery.
Good luck please let us know how you get on?