But it still works in Reaper, Studio One 3 Pro and Mixbus 32C.
 
I completely deleted the device (in Splat) and recreated it. 
 
I'mm 99% certain this happened after a WIN 10 update about a month ago.
 
Any other ideas?

I haven't set mine up for SONAR since switching to W10.
 
With 8.1 I used azctrl for FaderPort and when it would fail to initialize on SONAR startup, I had to exit SONAR, start Reaper, exit Reaper, then restart SONAR.  This was usually right after a machine reboot.
 
Maybe try different USB ports and double-check the USB power settings in Device Manager.  My machine reverted this and a few other settings when it updated to 1703 (Creator).
 
An extreme measure would be to uninstall everything FaderPort related from SONAR, reboot the machine, reinstall FaderPort stuff, restart SONAR, THEN reconfig SONAR to use the FaderPort.

You probably have already bapu, but just make sure channel and note aftertouch is still selected in Sonar preferences. They were deselected when I updated a couple of months ago.

Thanks to both of you. I'll check all that out tonight when I get home.

I just got a Faderport and am trying to set it up.  According to Presonus, Win 10 Builds 1607 and 1703 don't allow manual registration or placement of DLL files.
 
https://support.presonus....ion-for-Cakewalk-Sonar

olemon
I just got a Faderport and am trying to set it up.  According to Presonus, Win 10 Builds 1607 and 1703 don't allow manual registration or placement of DLL files.
 
https://support.presonus....ion-for-Cakewalk-Sonar

Run an elevated Command Prompt, it works.
 

Elevated Command Prompt worked.  First I had to get the Sonar DLL file from the link at the very bottom of that Presonus Support page, which is also where a short video is of the process.  I missed that link when I downloaded the Firmware Update.  Now I have to read some more threads on getting the FaderPort to fully function.
 
Thanks again.  Apologies for the detour, babu.

There is an AZ control preset for the FP too.  Using it will allow some customization of the buttons.