FRDM boards get shipped with bootloaders which are not Windows 8 or 10 compatible.So you need to update the bootloader.
If you have a Windows 7 machine at hand, then it is best if you use that. I wrote several articles on that topic, depending on your host environment, for example:
https://mcuoneclipse.com/2016/08/01/bricking_and_recovering_opensda_boards_in_windows_8_and_10/
You might try to disable the Windows search service, see:
https://mcuoneclipse.com/2018/04/10/recovering-opensda-boards-with-windows-10/
The good news with the K64 is that the K20 on it is not secured/protected, so you can load/program it with a J-Link or other debug probe. What I have been using successfully is reprogramming it in my classes with the patched bootloader described here:
https://mcuoneclipse.com/2017/10/29/adding-a-delay-to-the-arm-daplink-bootloader/
This one has not failed in a single case for several years, and have been used in hundreds of cases with students in my labs :-).
I hope this helps,
Erich
