futaba trainer cable (buddy box cable) 2.8M

Hello I ordered 3 cable futaba trainer cable (buddy box cable) 2.8M . I tested them on a Futaba FF9 (Master transmitter equipped with a module 2.4 GHz) and a Futaba FF7 super (Slave transmitter, switched OFF) . None of the 3 cables works !
Please help.
Thank you