This can occur on occasion with imported Alumni. The Grad Year is tied to the Alumni Affiliation, and most often the absence of which is due to one of two causes. To see if a user has an Alumni Affiliation:

To see if a user has an Alumni Affiliation: 
  1. Navigate to Core > Users > Edit User Profile Data.
  2. Search for and select the user.
  3. In the System Information panel, select Alumni Affiliation.
User-added image

Once you have selected and are viewing the Alumni Affiliation, you should be able to resolve the issue in one of two ways: 

If the user has an Alumni Role, but no Alumni Affiliation:
  1. In the top-right corner, select Add.
  2. Select the Role to grant the user (if multiple).
  3. Select the correct Graduation Class from the Alumni Class Of drop-down.
  4. If desired, mark if the user should be granted an Agent role or if they are an Honorary Alumni.
  5. Select Save & Exit
Note: If the Graduation Class does not appear, you will first need to follow the steps to Add a year into the Alumni Affiliation choices.
If the user has an Alumni Role and an Alumni Affiliation:
  1. Select Edit next to the Alumni Affiliation
  2. Select Save & Exit without making any changes