If you haven't already, try these steps from the Micro Freighter manual:
1. Linking the transmitter to the aircraft for the first time.
a. Install a charged battery into the bottom of the plane.
b. Close the battery door.
c. Turn on the airplane first. The LED will flash.
d. Turn on the Transmitter next. The LED’s on the transmitter and the plane will flash.
e. Move the throttle from low to high and then back down to low. The LED’s will glow steady.
f. Turn off the airplane and then the transmitter.
g. The transmitter will remember this link for future operation.
Download the Micro Freighter manual here --->
Micro Freighter Manual