help with Yamaha PSR 540

[NoFO]

I'm working on a project with a client that has a Yamaha PSR 540 keyboard, and we are attempting to lay the tracks down as MIDI, but we cannot get it to transmit. He has ben unsuccesful on his home computer and other studios have not gotten ti to work, except one time a feloow got it to work, but then could not remember how. We followed the manual, and the MIDI cable and input work fine, we've been using them with a drum machine, so what could it be?

thanks in advance

Chris