Our site is vle.upm.edu.ph. Our users are using Moodle app to access the site. However, our users on iOS devices cannot connect to the site. Only Android users can.
I already browsed the Moodle Mobile FAQ page.
I also followed the advice here: https://docs.moodle.org/dev/Moodle_Mobile_debugging_WS_requests.
I followed the recommendations here: https://docs.moodle.org/39/en/Moodle_app_FAQ#I_can.27t_get_the_app_to_work._What_do_I_do.3F.