My Vespa ET2 will not start when it's off the kickstand. Starts fine when the bike is on the kickstand. Engine cuts out when i push the bike off of the stand.

I think you don't pull the brake lever - as newer vespas will only start if a brake is pulled for safety reasons....

I'm not familiar with ET2s but I had a similar problem with a Vespa 100 years ago. After hours of messing about i discovered a bolt had fallen and blocked one of the air inlets on the bottom of the frame. Was fine when i kicked it but when my bum was on the saddle it kinda 'sealed' around the tank area and starved the engine of air. As i say, i don't know about new ET2s but sounds kinda similar symptoms.