iBooks / Books Constantly Asking for Login (Mojave)

[HUGE AL]

Beginning a few days ago, the application keeps continuously asking for login information despite it being entered correctly.

 

[AcidSlide]

Beginning a few days ago, the application keeps continuously asking for login information despite it being entered correctly.

I'm also having this issue! It is so annoying, it just keeps on asking until you click "Cancel".

Anybody knows the reason this is happening?