why this png file is rejected??

Besides other issues noted, conceptually, I think the AI bot in this case went way out of control. I'm not sure what that object is in the lower right corner. I assume the red is ketchup, but what is the brown? 

I would guess that the refusal reason is “Quality Issues” so you should look for quality issues. For generative AI, this is mostly rendering errors and artefacts. For PNG files, you also have cutout issues.

The plastic look is not very mouth watering:

Checking your cutout:

Everywhere, where you see this bluish shadow, you have pixels that are not 100% transparent. For a correct cutout, you would only see the chequerboard.

A detail:

This appears to be an automated background removal. It is necessary to rework and rectify that, or alternatively, perform it manually.

zoom in to 150%. Several edges are jagged.