If a Luminate CRM transaction was processed in Luminate Online, it is not possible to change the Primary Campaign Source directly in Luminate CRM.

This is because the Campaign in Luminate CRM is mapped to the Campaign of the Donation Form in Luminate Online, which cannot be changed after it has been processed.  The only possible solution is to change the Luminate Online Campaign or Form that the Luminate CRM Campaign is mapped to.

You can find instructions on that in article BB744451.