Keyboard doesn't work on selecting boot disk macOS
This issue is a common issue experienced by almost everybody that uses bootcamp on a Mac. There are a few ways that you can try to fix/do.

Method 1

Have you checked the installed drivers on the bootcamp side. Launch the bootcamp application on the Mac and deselect disinstall windows 10 or lower versions. Then select the "Get latest drivers from Apple" and insert a USB driver inside the computer. 



Make sure that the USB is working well and formatted on FAT32. 
If you're experiencing issues try to format using SDFormatter that is free. Press the continue button and let it download the latest drivers. 



Keep the USB inserted and boot on Windows10. In normal conditions, Windows should recognize the driver data and launch it automatically but if it doesn't recognize, just launch it like another program on your computer via the USB drive.

After doing this process reboot your computer and the latest Mac drivers including the CD reader, keyboard, SD reader and many more hardware will work.

Method 2

Make sure that your keyboard is recognized by Windows10. Check your hardwares inserted/paired with the computer you're using through the control panel. If the keyboard is not seen here contact Apple Support.

Note: First Method should work and in normal conditions drivers are not working on almost every user out there.

Take care and let me know if you need more help.

Arda