Why can't I write a review for my booking?

It might be because it's pass the deadline. You are allowed to write reviews only within a month from the participation date. (You can refer to the participation date specified in your booking details.) Once one month is past from the participation date, the booking will no longer appear as "Pending" in your reviews menu.

It may also be because you haven't taken part in the booking yet. You can start writing a review only after participation.