[Zubersoft]

Without having more information, it sounds to me almost like one of those connectors is faulty. The problem is that we don't have enough information in order to understand where the fault lies. MobileSheets is just using Apple's CoreMIDI classes to do the sending/receiving of MIDI messages, so it's unlikely there is a software issue in terms of how the messages are being constructed (as MobileSheets works fine with other MIDI devices). So then we need to gather the following information:

1) If you use a different application such as SongBook+, do you encounter the same issue with sending the MIDI messages? This will just help us determine if it's isolated to MobileSheets
2) Do you have another tablet or device you can connect to the keyboard to test the MIDI connection? 
3) Can you try connecting over Bluetooth to the device? This would require something like a CME WIDI Bud or WIDI Jack.
4) Does the Roland Fantom have a USB MIDI input? Or does it only have the 5-pin DIN connection?

Thanks,
Mike