Issues Setting Up KS37 With Reaper

[cherkcom]

Looking for some help setting up KeyStep 37 with Reaper.  In Preferences > MIDI Devices, "Arturia KeyStep 37" is listed in both MIDI inputs (Enabled+Control) and MIDI outputs (Enabled+Clock).  But when I apply those settings I get the following error message:

The following MIDI inputs could not be opened:
Arturia KeyStep 37
The following MIDI outputs could not be opened:
Arturia KeyStep 37

The KS is on and plugged into the (Windows 10) computer via USB and recognized by MIDI Control Center.

Any suggestions?  I am a noob to both MIDI and Reaper, so perhaps I overlooked something obvious.

[Disto]

It's look like your keystep midi interface is already locked by another software. Try to close all app (same for midi control center) 

[cherkcom]

Thank you, that did it!

[Scryptitious]

In case anyone else has this issue and quitting other software (most importantly, MIDI Control Center) doesn't work:

I had to delete a controller I no longer use from the MIDI Devices window and then reassign the ID number of the previous controller to the Keystep 37. Once I did that, the error disappeared and my KS37 was recognized.

Also necessary: Enabling "send clock to output" in the MIDI outputs section of MIDI Devices if you want sequences to be slaved to Reaper. Equally important: turn that option off during ordinary tracking.

Now if only I could get the CC knobs to control Pigments and other software synths. So far, I can't seem to do a basic filter sweep with Knob 1, which is assigned to CC#74.