Email says not Registered

I am using student account, when I try to log in it says this email is not registered

There are two types of login for a student, one with email ID and without Email ID. If the student is added with an Email ID then the provided email will receive a signup link to register to Kneura platform. If the student has not clicked that registration link and has signed up then student might get the above message. There is also access to the admin to Resend the email Request if the student’s email has expired. The student has to click on the link in the email to register within 24 hours else the link will be expired.
b. For the student added without email ID , Kneura will generate a unique username with which student can login, where password will be same as the username.