When trying to repeat a session for a number of weeks ahead, you may see the target dates listed as busy in the first step. The reason is most likely one of the following:
The instructor is already teaching a class at that same time. An instructor can only teach one activity at a time.
The instructor is not available at that date & time. Availability is set per instructor in Settings → Studio → Instructors → (select an instructor) → Availability . See Setting when clients can book .
Before starting the repeat session flow, set the instructor filter in the top right of the calendar view, so you can see their availability at a glance. A hashed background means they are not available at that time.