You may be so close that your transmitter is "swamping" the receiver(just too much signal). Back away a few feet (maybe 5) and see if that helps. I'm assuming the antenna is fully up and not physically touching any part of the plane or rx antenna. Your rx antenna is fully deployed and not coiled or wadded up somewhere in the plane.

Has this radio ever worked or is it new to you? Make sure rx crystal is same channel as tx is marked. Are you transmitting in proper mode? PPM or PCM
Are the radios new or used and if used are Tx and Rx the same brand?