Seems to have stopped working.
I “made this mios secure” a couple of weeks ago and before that had no probs adding users, but now can’t (“Error adding user”).
Is it the “secure” status? What does it do and can I undo it?
Try stepping through MiOS. I am not sure if that will work, but might be worth giving it a go. Otherwise, I would suggest raising a requet for technical support.