The first thing to check is that you've typed in your email correctly. If you have typed your email correctly, read on to understand why this happens.
How can I have an account but be told I don't when I log in?
This issue is caused when you have set up an account with an email address but you then change your email address to something else in your settings.
Our system won't let you join Seneca again with the same email you used to sign up before. But the email on your account has now changed, so you can't log in with that email.
How to solve the issue
You should try logging in with another one of you email addresses that you may have changed your account to.
You will then be able to change your account email in your settings once you are logged in if you need to.
If you're still having trouble, let us know the email you're trying to sign in with and I'll help you out.