In order for your packshot to not be replaced with an AI packshot when using the Chat to Ads feature you need to ensure that the packshot is a locked layer within the template you are using:

Select 'Layers' on the right hand side and then lock the relevant layer - in this case the product packshot, although it could just as well be the background image being used.

By default, the Pencil uses all unlocked images as placeholders to regenerate.