[nobbioch]

If that were the case, no users would be able to send MIDI commands over any channels but the first, but that is obviously not the case. Please just connect your tablet directly to the second keyboard and send a MIDI command over channel 2. If that works, the problem is with the Miditech Midiface 2x2 and there is a configuration issue that you will have to resolve.

Mike

After a few attempts, I have now managed to control both keyboards via MIDI.

[Zubersoft]

I'm glad to hear that! If there is any information that would benefit other users, please share it if possible.

Mike

[nobbioch]

I'm glad to hear that! If there is any information that would benefit other users, please share it if possible.

Mike

As always, the problem lay with the user. 

The output port in the MIDI settings for the song was set to “All.” These must, of course, be set to the appropriate output port.
So, for Keyboard 1, set it to MIDI Out 1. For Keyboard 2, set it to MIDI Out 2. See attached images.