I'm trying to turn on the ability to use email address as the username when logging into a site. When I try to turn this on under security/user settings, all I get is a message saying "could not update registration settings. Please try later.". I thought perhaps it was bc I was using 9.1.0 so I upgraded to 9.1.1 and I get the same results.

Anyone know if there is a prerequiste to this setting or even what table this lives under in the db so I could change it manually?