If a student is reporting that they are unable to sign up for a scheduler event while other students can sign up successfully, it's usually an indication that the student has not enabled the course calendar in their view.
To enable the course calendar, see the steps below.
- Click Calendar on the lefthand navigation
- Click Scheduler
- Find the title of the event and click "You can sign up for this"
- On the right-hand side of the page, make sure the box next to the course is enabled (it is enabled if the box has a color corresponding to the course - see screenshot)