For security reasons, LastPass is requiring that you verify that you have access to your email account. This check should take 1 minute and will ensure your security.
This will continue with each new location you try to login with until you change your master password or select that you're comfortable with how strong your master password is.
For more details see this blog post.
To re-enable your account:
Enter your email in the below box. Click 'Send Email' to have LastPass.com send you an email containing further instructions. If you do not receive the email or experience issues, please check your SPAM folder. If you continue to have problems, email us at support@lastpass.com for assistance.