Bookings calender not showing bookable events

I have a booking calendar with multiple services and different staff. The services are, by default, not bookable, and the staff are set to ‘events in the calendar do not affect availability.’ We have scheduled training sessions, and it has worked well. However, we have now discovered that some services no longer appear as available, even though they are correctly listed in the calendar. Is there any way to resync the calendar to resolve this issue?