How to add Apple Wireless Keyboard as a bluetooth device for BootCamp 5 using Windows 8.1 and or Windows 10?

My computer is a MacBook Pro, 13-inch, Late 2011 model. I use an external 27" monitor, and bluetooth trackpad and keyboard. Until the last week of July, 2016 I was using with Windows 8 with BootCamp 5, nicely. Then I got a message that Windows 8 wouldn't be updated for critical and security updates. I decided to upgrade to Windows 8.1 but the wireless trackpad works intermittently, and the wireless keyboard hasn't work at all. I get a message to pair it, but pairing is always unsuccessful. Then I upgraded to Windows 10 and same issues with both trackpad and wireless keyboard.

Anybody has a fix? Thanks