Purchasing books on apple books

Apple books permanently lost many functions related to buying books online, leaving my app effectively only with two tabs, one for my already existing library of downloaded books and one for search, which only searches in my library. i have a screen time limit, but i turned off all restrictions.

I also checked if purchases for apple books are authorised on my iphone, and they are. i don’t know what to do, and i can’t really remove my restrictions. what i also don’t understand is why it doesn’t allow book purchases but allows any purchase elsewhere on the phone, when i explicitly disabled any restrictions.