Are you using the official release from 17 October 2017? If so download the pre-release version from https://teamcity.projectpokemon.org/login.html
Choose "login as guest", and then go to Save Editors -> PKHeX; choose the latest Windows build, by clicking on artifacts, and then pick the zip with the exe and DLLs.
This is a direct link: https://teamcity.projectpokemon.org/viewLog.html?buildId=16473&tab=artifacts&buildTypeId=PKHeX_BuildWindows
Just login as guest, and choose the correct zip. Also be sure to make backups, just in case, because it's unstable it can possibly corrupt your save.