Had the same issue, due to lockdown the Trackdays got booked very quick however I have 4 evenings (I like evening as does not interfere with work) but to get them I was on reserve list. You have to go on reserve list on every date. It’s a pain they do come up. Had email at 5.30 today to say a cancellation has come up for Tuesday and can be booked via website. Not sure if it’s still there now tho?