If gyro/mixer keeps flashing between red and green even after you switched off Tx (motor unplugged to avoid unintentional motion), then your Rx/gyro/mixer probably finds a fault at initialization and comes to a halt at that stage. Whenever working properly but doesn't receive signal (like turning off Tx), the Rx/gyro/mixer LED should stay red solid. If you don't have another set of Rx/gyro/mixer for diagnostics, I would suggest getting the shop you bought the heli from to do more diagnostics if possible. Otherwise, I can only suggest trying anything that "might" make that flashing red/green go away. For example, unplug all servos and motors and try again. Or unplug the Rx crystal and try again (not sure if that's a bad thing for the electronics though). Or if you have the later "separable" Rx/gyro/mixer box, unplug the gyro/mixer connectors (channel 3/4) to the Rx. Have you ever unplugged the servos and/or gyro/mixer connectors and accidentally plugged them backwards?