You don't mention radio type, if it's a computer radio have you changed to another model? If so make sure you're still transmitting PPM, and not PCM.

Is the battery fully charged? You mention a kit, I assume a flight pack?

Try and connect the battery directly to the receiver without using the switch harness, see if that cures it.

Try and remove and re-seat the crystal. It could be possible you got a bad crystal, unlikely, but possible.

If all else fails, ensure your transmiter is still working with your old radio....

And last possibility is you got a bad receiver, take it back to store.

HTH..

Andy