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.