Fix it
A learner cannot join: checklist
In short
Check the time, the meeting link, the learner's access and the date, in that order.
A learner says they cannot get into a live session. Check these, most likely first.
Still stuck? Copy the join link from the session's Join link card and send it to the learner.
The time: Join now is grey until 15 minutes before the start and after the session ends. Hover the button to read the reason.
The link: "The meeting link hasn't been set yet" means no link. Open the session with Manage and add one. For Teams, "Teams meeting not created yet" has a Retry button.
Their access: the learner needs active access to the course. Check the course's Users tab for an expired or removed enrolment.
The date: look at Dates on the session page. A removed date cannot be joined, and a repeating session may show learners only its next date.