I've placed an appointments + signup calendar on a page that only specific users of the site can see (this requires them to have signed in and the restrictions are set using the User Access Management UAM) plugin from the wordpress repository.
The problem is that when I require a log in to make an appointment, I get a little window saying I need to log in (which I already am). I am also not given any option to login despite having set that option in the settings. This acts like it's a conflict of some sort so I'm wondering if you've run across any plugins that cause this problem.
By the way, thanks for adding the additional break times option to the work schedules, this made my life much easier.