[vunderba]

You didn't do anything wrong - Kling can occasionally return a static result particularly for 2D images. It might have been the "grid lines" but Kling's model is effectively a black box.

https://kling.kuaishou.com/en

Side note: Nice video - setting up the rigging mesh reminds me of the "puppet warp" deformation system in Adobe Photoshop.

@Vic:

Bit of advice, you need to build some kind of a static checker (either in terms of the total compressed size of the video - very small file sizes likely indicate a failed gen, or in terms of a hash as a measure of frame-to-frame changes) - to help set up an automated appeals for customers... having to manage this on a case-by-case basis will destroy any enthusiasm you might have for this project.