bend it back away from the trigger so it makes a V...
stick a tiny allen wrench in the middle then carefully push the top of it back away from the trigger. Or adjust the trigger adjustment screw so there is more play in front of the trigger. If none of these work you may have a bad microswitch.
The metal flap is pushed by the trigger which then contacts the switch and fires the gun. If there isnt enough contact or pressure the gun wont fire. If after you do this and it still doesnt work you need a new microswitch.