Received internal error trying to add user to course not it will not allow me to add any user to course says it cannot see email address.
I too am having this problem; just started today. I'm using Canvas Free for Teachers version. The message I get is "We were unable to find matches below."
I've just tried unpublishing one of my courses (so I now have three published) and it now seems to be working. I can't see any limits about the Free for Teacher account regarding number of published courses, so perhaps it was just a momentary glitch in the system (fingers crossed!)