There can be many compatability issues between the TX and RX. AM vs FM, Pos vs Neg shift, wrong crystals in one or the other and others. You have most likely assembled a combination that will never work as it is. If the plane came with a RX, put it back in.

If this http://www.nitroplanes.com/new204chathi1.html is the plane you have and you are using a 72 MHz RX then the problem is that the plane comes with a 27 MHz TX according to the literature.