Hi,
Well, there is a LOT going on here, and it's entirely possible you aren't aware of what all is involved here, so indulge me a bit and maybe we can get this sorted...first I want you to go to your "My Presonus" account, and start a tech service ticket. I hope I don't have to tell you what that is, and if you haven't done so, you NEED an account... and you need to register ALL your hardware and software. If you do start a tech ticket, and don't need it, you can always cancel, but they are VERY busy guys and it can take a while to get to your questions...
Then, (if you haven't already, go to your hardware account, and software account, and download the latest software, and drivers....The drivers will help your interface (AB USB) work with your software... (your OS and Studio One) ALSO install Studio one from your account... not form a disc or wherever...... THIS IS EXTREMELY important if you want a trouble free experience...If you have done all this, forgive me, this is what ALL the information is about...
Now, we need to discus the AB USB... this is a PORT SPECIFIC device, and as such will ONLY work on the port it was originally installed on!!! (critical) I you have, or THINK you have plugged it into ANY OTHER USB port, you will need to uninstall and re-install the AB USB drivers (the ones in your account ...specific to your OS). You need to know about the Knowledge Base:
http://support.presonus.com/forums
In the KB, you will find a TON of helpful stuff! so make it your friend!... here is the link to the AB USB section:
http://support.presonus.com/forums/20568841-AudioBox-USB
There you will find the info necessary to do the uninstall, and re-install, and some tips on the AB USB... note, that there is a whole section about recording with Studio One as well...
Now, within Studio One, if the keyboard shows up but doesn't function, or is barely functional, it's possible the keyboard has an issue... again, the Tech ticket is you friend here.
At this point the ball is in your court, we can lead you but you have to do the work...and it's a bit of a steep learning curve if you don't know anything about DAW recording...