Elbert

I've tried everything to connect an ipad to a ctk-720 with the usb midi port but so far no luck. What could I be doing wrong, I know the ctk is old but still has the usb port to use for connecting as a midi keyboard. The strange thing is that it works on my Mac pro air using just a "printer" cable but is doesn't work using the same cable and a lightning camera kit for the Ipad. Help!