I'm using the binary you provided here.
I had a repo with git-crypt initialized already. git-crypt unlock key suggested me to migrate the key, which I did w/ git-crypt migrate-key. git-crypt unlock new-key hangs silently. I'd waited for about 3 minutes before shutting it down.
The output in Process Monitor looks like git-crypt is stuck in loop, polling some system folders which I don't think it supposed to be polling. I could email you the full log, if it helps.