To bind the 3GX, insert the bind plug into the bind port on the 3GX and power on the helicopter. The satellite(s) should be flashing rapidly. Now, hold down the trainer button with your sticks in the fail safe position on the Tx and switch it on. The lights on the satellite(s) should start flashing slower, then go solid. Once they go solid, pull out the bind plug. Do not power off anything until after you pull otu the bind plug and the 3GX initializes.
If this is the process that you are following, then you may have an issue with the Tx or Rx that only JR can diagnose.