I had a similar problem when I changed my fuel filter the other day.
Take off the air filter and gently push down on the flap. You should hear a squelching.
If not, there is an air lock somewhere.

I got it going by cranking the engine over with my foot flat to the floor for 5-6 seconds at a time. Once it starts to catch, come off the throttle.

Apparantly the RS starters arent amazing, so dont keep cranking for ages! (this might be rubbish, just what I was told)