From your 'My Hub' page (please see below)
On the left hand side of your account, you will see the side menu in which you can select 'Calender'.
This will then show your calendar with all sessions/events booked in
You can then simply select any of the recurring sessions and hit the 3 horizontal grey dots to 'View' the details.
If you click the 3 horizontal grey dots next to 'Details' you will have the option to edit or cancel the session.
And this will allow you to cancel/edit one or all sessions/events.
same way as i do it but not working again