This error indicates either a custom designee or the default "write-in designation default" designee needs to be cross referenced. To resolve this, you will want to:
  1. Cross reference the designee mentioned in the error
    1. Select Data Management > Luminate Configuration
    2. Click Cross References
    3. Click Configure next to Gift Designation
    4. Click Create (Or Configure) for the appropriate desginee under the Items Not Referenced tab
    5. Select the appropriate value from the External Mappings Designation section
    6. Click Finish
  2. Rebuild the Errors