Books Won't Open on iMac

Many of the books in my library won't open on my iMac. The books came from Apple's store and were originally purchased on a very old iPad (which still works!). The books were transferred from the iPad to this iMac (27 inch, late 2015, OS 12.3.1). The books appear in the library when Books is opened, but clicking on many of them does nothing while others open. I'm also confused because, in the sidebar, the "Books" section under "Library" seems to contain all of the books I've purchased. However, "My Books" under "My Collection" contains less than half. I haven't tried opening any pdfs collected from other sources.

Does anyone know why all of my books won't open? Appreciate any help.