You signed up for a 30-day trial and got a key sent through. When you enter the key into MailEssentials, it says it's already expired.
You may need to reinstall MailEssentials, as the trial key requires a new installation of MailEssentials. Trial keys only work on servers that the first installation was done less than 30 days ago.
If reinstalling did not work, you may contact GFI Sales and request a license extension.
A previously licensed installation will not permit the use of a trial license key.