Address merge fields will not populate with data if the address itself is marked as Mail to this Address = No. To resolve:
  1. Go to Contacts > Individuals
  2. Search for the supporter
  3. Manage Contact
  4. Click the Profile tab
  5. Click Addresses
  6. Edit the primary address
  7. Set "Mail to this Address?" as "Yes"
  8. Save changes
  9. Redo batch Acknowledge