Futaba 4PV link problem
 

Just received a new 4PV (transmitter only) and tried to link it to one of the two R334sbs RX (compatible) that came with my 7PX...no joy.
Transmitter is set to correct protocol...(T-FH), put TX into link mode and get 20 sec timer, power up RX, within 50cm, red light on, press switch 2 seconds red light starts flashing....that's all that happens. Never get anything other than flashing red. I don't have anything other than the battery plugged into the RX. Tried different model locations in TX. Tried different protocol. Should be super simple but I can't figure out what I am screwing up. Any ideas?