Starting left engine right engine turns off vice versa?

Master Ignition is turned on, Prop and Mixture are at max, throttle levers pushed forward a little bit.
left primer, energize left (wait a few seconds) mesh left and prop starts. But when i do same with right prop left prop will turn off. And if i do nothing after some time prop turn off. What went wrong?

Fuel Selectors were set wrong. Shame on me :frowning: