I view the readme homepage of the client. It has no indication of DALL-E 3, and shows an example of 256x256 image generation.
The CreateRequest.php was last updated March 1 2023. DALL-E 3 API was nonexistent then.
Chiefly, it fault is that it does not pass a model parameter and therefore cannot specify dall-e-3. You will need to modify this languishing code.