Q: Does it work with all other plugins disabled with a default theme enabled?
Both plugin and WordPress are updated to the latest available version, the same setup works without any issues with another blog on the same server. Here's another thing - if you try to add accounts for individual user, that works. It seems the only thing that doesn't work is where you set up accounts for all users. And it has worked before - I was able to add accounts there, but then all of them just vanished and I can't add them anymore. I can't figure out what triggered that. Also - I've tried to enable logs, but they don't output anything anymore (they did before and they do for individual profile setup).
I can provide an access to the setup I'm working with, if you like. Just send me an e to firstname.lastname@example.org