Maybe a simple recheck may help, i would recommend checking in this order :
- Unplug/replug everything and make sure all cables are doing their jobs.
- Restart your computer, plug your keyboard in and launch SO
- Check if it recognise it, if not , set it manually in the midi peripherals section.
- Once it's recognised by SO, just make sure you are in rec ready or input monitoring and play some midi in a inst track.
- If still not working, you might wanna check the specs doc of your keyboard to see if there is maybe a special mode enable or something more to do.
Hope this will help;