Personalized Merge Fields
From LongJump Support Wiki
Personalized merge fields such as "First Name" and "Last Name" should be written as {FIRST_NAME} and {LAST_NAME}. Note that, as a general rule of thumb, a merge field is simply the name of the field surrounded by {}. So city would be {CITY}, state {STATE}, and so on. Once you've corrected your merge fields, you can re-launch your email and everything will be good to go.