This error occurs when one of the records being merged does not have a valid Convio ID (often it is 0, or is missing).

To resolve this, do the following:
  1. Go to each record in Luminate CRM that is involved in the merge.
  2. Find the Convio ID and compare it to the associated record in Luminate Online (it may be useful to search Luminate Online using the Luminate CRM ID).
  3. After you have identified the Luminate CRM record with the Convio ID that does not match a Luminate Online, replace it with the correct ID from Luminate Online.