First, check your emails. If your student has canceled the lesson, an email notification should be in your mailbox. Look into the Spam folder also, just in case.
If you don’t see anything about cancelation, just wait for 15 minutes. If your student doesn’t turn up during that time, you can close the meeting window. The lesson will be considered complete, and you’ll get the payment. If within 15 minutes your student enters the meeting, and you have the lesson, you may finish it as scheduled. Of course, you may also finish later, if it’s convenient for both of you.