Client did not recieve zoom link for meeting

Hi all, I use Calendly to organize my meetings with Zoom. When my clients pick a date from Calendly, they choose Zoom meeting, and Zoom is supposed to send them a link 30 minutes before the meeting takes place. Recently, some of my clients have either missed or been late for their meetings because they did not receive a link from Zoom. Has anyone else run into this issue?  Appreciate your time.