I honestly wouldn't bother with Flightcrew any more. We've already been debating whether to abandon it altogether.
Having said that however, I know of know reason the latest version from:
https://github.com/Sigil-Ebook/fligh...eleases/latest
wouldn't run.
Just make sure you're downloading the zipped plugin for Windows (if Windows is what you're using).
It certainly works for me on my various machines.