Starting from an image
Up to 4 images, as a first frame, a last frame or a style reference.
You can attach up to 4 images. Each has a role: a first frame is where the video begins, a last frame is where it ends, and a reference guides style without fixing any particular frame.
A first or last frame fixes the output's aspect ratio to that image's — the provider takes the ratio from the image and rejects any other — so the aspect control is hidden when you attach one. That is not a bug; it is the only ratio that render can produce.
The provider refuses photographs of real people. Any image that reads as a real person's face will be rejected at submission with "may contain real person", and nothing is charged. Describe the person in the prompt instead, or use a clearly synthetic image.