Attendees aren't able to access previously scheduled meeting.

Our video conference meetings take place in the U.S. More and more, if I schedule a call in advance, when the time comes to meet, I (as the host) can join the meeting, but the attendees can't. They see a screen that say, "Please wait for host to start the meeting". Those who chose to call in are having the same issue. If I send a fresh link in the moment, it works. What is happening?