Dear David ,

Im really sorry to say that as per CBSE board rules those students are had given the board exam in March 2019 are eligible to give improvement exam in March 2020 (along with other students). But if you are passed out in 2019 then you had a chances on 2020 march and as per date was gone but you will not consider in 2021 like you have to appear the test between 1 year.

I hope you will understand

Thanks