In order for the first name to pull through there must be data in the contact field of your contacts. You can check this by going to Audience -> Contacts and searching the email address of the contact.

Testing your email in the GatorCreator Test Centre will not test dynamic content like a first name field as the test centre is simply for testing the design of your email.

Please ensure you are mimicking the correct contact when testing your email. In the Campaign Testing tab it is easy to forget that you must choose which contact you wish to mimic if you want to test a specific contact.