You can only report a score for a Public Match, a Private Match or a league match. A Court Booking is described in the app as "Regular court booking. No score reporting or implication on player's levels."
Next time
If you want your score to count, choose Public Match or Private Match on Select booking type when you book.
Good to know
A court booking can't be changed into a match afterwards.
Report score appears on a match once it has ended.
Tennis match scores are recorded but don't change your level. Only padel levels change from scores.