Add a watermark on a pdf with ilovepdf

Hi,
I am trying to build a scenario that automatically adds an image (with a signature) to PDF documents

The first module, see if there are any new pdf files in a Drive folder.
The second module, downloads the signature from a Drive folder
The third module, adds the watermark on the document with IlovePDF
However I always get an error from this module and I don’t understand where it is coming from.

: [400] This task can’t be processed. Check why in the params. || ||

.

Can anyone help me ?