That’s very weird. I re-installed multiple times and the keyboard has always worked right off the bat. These systems are really finicky though.
What you can do as well is download the re-installation bundle from Teclast. Go here: http://www.teclast.com/en/firmware/
Type in the ID of your X5 Pro. Mine was k3j2. Download all 3 parts, and write the binary file to a USB thumb drive. BEWARE, anything that boots from that thumb drive will be immediately wiped, formatted and have a copy of Chinese windows 10 installed.
Using that, see if the keyboard works again.
You might also be better off just sending this thing back. The keyboard should be working without any need of drivers, etc. You can also try installing the updated firmware and drivers from this site. https://techtablets.com/downloads-drivers-roms/