Why subscription link stopped working from Facebook ad post

I set a facebook ads campaign with the subscription link provided by zoom webinars, now, suddenly it stopped working and people can not subscribe from the link that 15 days ago was working properly.

The last time i launched a webinar, happened quite the same, when i started the webinar, my susbscribers could´nt conect, they said that , when they pressed the "join webinar" button from the confirmation e.mail sent by zoom, there just show the message "waiting till host start this webinar", but it has already started

i have not changed the suscription link , could somebody explain me why is this happening?