This message "KitProg version Expecting 2.20, but found 2.21."is just for information, it's not error.
You should be able to use Kitprog for programming. If you are not able to program, please update.
Please follow the steps mentioned in topic "Updating the KitProg Firmware" at page #11 of this Kitprog User Guide available at the following link:
I will try the operation again but it looks and behaves like an error in many places.