This error happens when the user running the merge does not have the Document object enabled in their Apsona Configuration, even if they have Salesforce permissions and the merge works for other users. Apsona merge buttons execute queries against Salesforce objects, and if an object like Document is not visible in the user’s configuration, Apsona cannot query it and returns INVALID_TYPE. To fix the issue, edit the user’s Apsona Configuration, move Document into Visible Objects, save, and clear cache. Once the object is visible to Apsona, the merge button runs normally without requiring changes to templates, code, or permission sets.