The latest version/any recent version of Signal Desktop should work.
My best guess, currently, is that you were also affected by the HTTP 500’s, and that therefore you didn’t yet sync any profile key information.
Either that, or you’re somehow on an old version of Whisperfish (maybe double check in About). If you send some 1:1 messages to your buddy, then wait an hour or so, it should work. If it doesn’t, I suggest you get in touch with me on IRC/Matrix/email; it’ll get quite messy here otherwise 