Without apparent reason CbB will randomly ignore the MIDI Keyboard connected via USB. The MIDI input/output indicator is then dead.
 
The Keyboard does show up in Preferences > MIDI Devices.
 
After restart of CbB everything is fine again.

Check the Power Management options in Device Manager.  Look at all the USB ports/hubs and make sure the computer can't just turn them off to 'save power.'

And check them with each WIN 10 update, as Microsoft appears to randomly reactive different power options, especially for the USB hubs.
 
 

I'm on the "High Performance" plan.
USB selective suspend setting: Disabled

If you have google chrome running that can hijack the midi drivers.

Also in device manager, make sure all USB entries with the word "hub" has the setting  “Allow the computer to turn off the device to save power” disabled.

the other things I have tried are using a new USB cord and trying a different USB port if you can.  Also check that the drivers that show up for your device in device manager are the most recent ones.  I have seen where an update to WIN10 has Windows installing some older device driver on a device.  Also the 'fast start' and hibernation options for Win10 have screwed around with my USB ports.  Making sure both of these are also off may help.  
 
let us know if anything works.  That would be helpful for the next person! Cheers!

I regret to have to say it but it's a Cakewalk problem.
 
I tried with Reaper: I left it for 30 minutes. Monitor turned off after 8 minutes as set by me in the power plan. After 30 minutes, I struck the keyboard and it played.
 
Tried the same experiment with Cakewalk: after I came back 30 min later it was dead. Midi Activity indicator dead. Keyboard DID show up in Device Manager though!
 
After I restarted Cakewalk all was fine again.

My experience is that if the keyboard uses a generic widows midi driver this will happen. My Roland and my Yamaha come with drivers, they never get disconnected. My Akai synth station uses a generic driver and always gets disconnected.