Appointments+ not displaying available time when selecting a service

I have installed Appointments+ and it shows on the frontend, but when I change the services "show available times" is not working. The available times are not displayed when selecting a service.

I tried deactivating all plugins and switching to 2017 theme and I’ve found that the issue is related to the custom theme I’ve developed for the site. I started it with WP_Bootstrap_Starter and I’m using jquery-1.12.4 on it, not sure if this could be related to the issue.