Photos and Video will not drag and drop when editing ebook via online ebook editor. HELP?

Uploaded photos and videos, want to add them, switch out some photos.

This was a book previously created via booksmart and now online and an ebook.

Able to change text.

Can’t change out images – can either remove them entirely, or leave them as is. Can’t swap photos in the photo box on the page, nor can I add new photos.

I’ve even created some new blank pages and can’t drag and drop. I don’t even get the 4 directional arrow cursor – just an arrow.

So, what’s up? I’m on a macbook pro, latest OS.