If you're interested in a lesson that is currently sold out, you may want to subscribe to a vacancy notice. Someone can cancel their reservation before the lesson making new reservations possible. In that case, you will receive an email notification and can make a booking.
While browsing the lessons on the business' Booking page, you can tap a sold-out lesson and select "Subscribe to email":
All lessons you have subscribed to receive an email notification are marked separately with 🔔 on the Booking page.