iBooks Apple ID sign in prompt accepts my password but fails and re-asks, repeatedly I am on a new MacBook laptop running 10.14, and trying to sync my book library on iCloud to the Books app.

When I open the Books app it asks me to sign in to Apple ID, and it accepts my password. But then within about 5 seconds the sign-in window appears again, as if for the first time. It doesn't say the password or ID is wrong.  Typing in the password again has the same effect.

It does this over and over, and it doesn't seem to have signed me in, and so my books never get downloaded to the device.

Despite the books not being downloaded, the Books app identifies my iCloud "collections" in the side bar, but the collections are empty.

Also the Books app is showing me a preview of what my old library looked like on my old laptop (which I no longer have access to) but doesn't show any of the new additions to my iCloud library made on my iPhone. 

Anyone have any suggestions? Thanks
I had the same problem in Mojave. I managed to solve it by going to the Store menu in Books, selecting "Authorize this computer..." - which it did, and suddenly all my  books appeared in Books. After this Books works fine.

(my Mac was already authorized prior to this, since I had no problems with iTunes for example)