icloud books not saving to phone or appearing on ipad

I am signed into iCloud on both iPhone and iPad. Both devices have iBooks iCloud sharing enabled. Both devices are fully updated. I have restarted both devices and the problem remains.

I have several lectures from school saved to my iBooks app on my phone. I have backed them up to iCloud so I can access them on my iPad. My iPad Books app is empty despite being fully connected to iCloud so they are simply not transferring over. My iCloud storage is not full. These books cannot be shared by airdrop or saved to my files so I’m at a loss on how to get them to my iPad.

Similarly, on my iPhone I believe the lectures are downloaded as they do have the little cloud symbol or have the option to download when I select them. However, when I unselect iCloud Books sharing in my settings, all the books disappear. They reappear when I toggle the setting back on.

Please let me know how to resolve this!