Sorry to hear about the recent issues you have been experiencing.
In this setup, and for that keyboard, the Korg should not connect to the AudioBox at all, it should connect directly to the computer using its built in USB MIDI connection. Connect it and make sure the OS recognizes it.
1. In Studio One, the AudioBox iTwo will be used at the Audio Setup > Audio Device window as the Audio Device (Windows), and on OS X the Playback and Recording Device.
2. For the Korg, you will need to go to Options(Preferences OS X) > External Devices and create a New Keyboard with the MIDI "Receive From" assigned to the MIDI port the Korg is connected to. You don't need the MIDI "Send To." Set this to Default Instrument Input. Make sure none of the MIDI filters are checked.
Here is more information on the subject: http://support.presonus.com/hc/en-us/articles/210050203-Basic-Midi-Setup-New-Keyboard-Control-Surface-Instrument-Faderport
Please create a support ticket if you would like to discuss this in more detail.
We also encourage you to create a thread about this on the Presonus user forum. https://forums.presonus.com/viewforum.php?f=108
This will allow for back and forth discussions about an issue or question and more points of view as to possible different approaches or workflows.