[Zubersoft]

If you change the MIDI library to High-Performance, or Default, do those work any better with your PA600? If you uncheck "Show only MIDI devices" and try to connect after doing that, are you able to connect successfully? To provide some additional information, if you have to uncheck that box, it means the keyboard is not a MIDI-class compliant device, which means it can be more difficult to interact with it (i.e. a driver is required on Windows to connect to it as it doesn't use the generic MIDI implementation). 

Did you try pairing your tablets in both directions (i.e. initiate the pairing from each tablet to see if either behaves differently)? Normally if a code is shown, you should see a popup on the other device asking if you want to allow the connection.

Mike