Solved! keyboard or mouse sleeps. One keystroke wakes keyboard up.

[markireland]

Either my keyboard or my mouse sleeps. One keystroke wakes keyboard up. The keystrokes seem to fill a buffer and there is a delay before I see them often with the first one missing.

I am on Win 10. I have tried all the advice easily found with a search.

 

[Prostar Computer]

Are they wireless? What's the make/model of both?

 

[ElectrO_90]

Make sure you don't have power saving mode on, put everything on max power usage
Control Panel\Hardware and Sound\Power Options\Edit Plan Settings
Change Advanced Power Settings
USB setting Disabled
or change to high power
anyway try that

 

[markireland]

Are they wireless? What's the make/model of both?

Yes, both wireless. Logitech K270

 

[Prostar Computer]

Pretty common behavior on wireless peripherals. It does so to save battery power. You can try disabling the "USB Selective Suspend" feature in the Windows Advanced Power Settings, though it might be how the devices were designed to behave.