my fiat 500 is not starting its making humming noises and clicking is coming from the engine fuse box, there is an anti theft warning light and it is saying fuel cut off. i have had the key and barrel checked and all is fine with this, its not the battery and yes i have petrol in. can anyone point me in the right direction. The car has not been in a crash nor has anyone tried to break in,

If the inertia switch has tripped then that has cut off the spark and the fuel.

You can reset it by following the picture below. Has it tripped for a reason though?

I always use MES to do it as I’ve found that the indicator method doesn’t always work.

What age is the car, is it a automatic, the clicking noise, does it do it with just the ignition on rather than trying to crank the engine?

Humming likely fuel pump-clicking is a relay. The cutoff reset only works in USA, not UK. If the immobiliser had cut in, it would turn over but not start (disables injectors and spark). Do you have aspare key you could try?