Thank you for contacting Presonus Technical Support. Sorry to hear about the recent issues you have been experiencing.
There are some customers that have gotten this device to work with Studio One.
Please take a look at this article from MOTU's tech support. http://www.motu.com/techsupport/technotes/document.2001-03-20.8063592446
Let me know if this resolves your issue. You may want to reach out to MOTU and see if they have a solution for you. When you create a new MIDI keyboard for a MIDI device that you have plugged into your MOTU, you should see the MOTU as an option inside of Studio One for your send.
If the issue remains, please create a ticket to technical support.
Here is a link to create a ticket: http://support.presonus.com/hc/en-us/requests/new