but I think there should have any placeholder image, so somehow we forgot this, the AMP does not have the same error as the plugin most specifically related to AMP features.
You can check portfolio post type after activating of this plugin. you need to add new portfolio item in edit or add new item you can see feature image sectio, you can upload here portfolio image.
Thanks for your kind of review, sorry for problems that you feel, I didn’t change theme style through plugin, can you provide link or screenshots where you see issue so I can solve it.