Try these three steps:

1. Ask the teacher to please check their SPAM folder. If it's not there, please contact us and also advise your IT team to permit our email domains: @classcreator.io and @notification.classcreator.io

2. Check that the teacher's email address is correct on the Manage Teachers page.

3. If everything is correct, try resetting the teachers password as an email should be sent to them automatically.

If that doesn't work please contact us.