I have serveral participants who can´t enter my study (after they have received an email) although there are enough places left. I get messages like this (see below). Any idea what the problem might be?
Thanks for your help.
I got a mail with an invitation to this study twice but I can’t take part in it because the notification says ‘You are ineligible to take part in this study.’ I’m not sure if there is some kind of technical problem.