Error: “INVALID_ARGUMENT”
If you have selected “Bulk Image Merge” in your Document Action and any image URL is invalid, the document generation will fail and you will see an “INVALID_ARGUMENT” error.
To troubleshoot which image URL is causing the document generation to fail, remove all image merge fields from the document template. Then, add one image merge field back at a time, testing the document generation after each new image merge field is added.
See this article for more information: Template Configuration