Are you receiving a message saying your account has not been verified?
When you sign up for a Gliffy account, you should receive an email with the subject "Welcome To Gliffy!". If you did not receive this or deleted it, click the link to resend your confirmation email.
Within this email there is an orange "Verify Your Email" button. Clicking on that should verify your email.
Below the orange Verify Your Email button is a confirmation code. You can also copy this code and enter in the confirmation box manually.