OK, big mea culpa here. It appears the user accounts were not included in the migration to the new hosting service.
Thankfully there weren’t that many of them to begin with, but what few there were will now need to be recreated.
My apologies for the inconvenience. If I get the chance I’ll see whether there’s some way to export that information from the old system but please don’t wait on that. If you’d like to post a comment feel free to just create a new account.