Allowing already registered users to book without log in

Hello !

I’m a bit stuck with a setting I think I don’t fully understand:
I deactivate the “booking without user” mode, creating users each time a new user booking from the website.

BUT I would like users to book again without having to log in the website, because I think the users (social workers) will never remember theyre passwords… So I activate the “Allow bookings from a known address“, but when I try to make a booking without log in, I get the login error.

(And now, when my settings are “booking without user mode” = YES and “Allow bookings from a known address” = NO, I still can make multiples bookings with the same email address… I understand no more the operation ??)

Heeeelp!