Try entering your mobile number as the username rather than an email address along with your password. If this allows access, then click into the Profile tab and check your email address is correct. If your email address is incorrect you can update it. If your email address is missing, then please add it to your profile.
I still can’t login?
Contact the school and ask them to verify that they have the correct email address and mobile number on record. If the details are correct, then please request a new invitation. Please ensure you are clicking on the correct icon for your school.