Cancellation can be done only for the "Confirmed" booking, when Travel Desk cancels a confirmed booking pop up asks to enter Refund amount.
In case where request is "Approved" but booking details are not uploaded, then first booking details have to be entered only after that booking can be cancelled.
For step by step guide please check 3 min video here - - https://youtu.be/izLhxLXU1Bw