Blocks defined by the Woocommerce reservation client that do not work

I created a product and configured all my availability settings (Global and product) in Time interval (All week) from 8AM to 8PM. My reservation product only allows the user to select a date and the time selector is never displayed. The time selector will only be displayed for the user if I set the Duration of the reservation in "Fixed blocks" but I need to configure it in "Blocks defined by the client".

Here are all the configurations for the product:

general

Availability

cost

This is for a spa and I am simply trying to allow users to book no matter how many hours of spa treatment they want between 8 a.m. and 8 p.m. If I enable "Blocks defined by the client of 1 hour", the user sees this when he clicks on a date in the calendar:

Reservation calendar

Note that there is no time selector. Only if I change the option of the product to "Fixed blocks of 1 hour" appears for the user.