You were due to pay preliminary tax for 2019 in Nov 2019 and the balance in Nov 2020 when you submit your final 2019 accounts
However, the preliminary tax due can be based on your 2018 tax, which you said was zero. So no preliminary tax for 2019 due
In Nov 2020 you will have to pay the tax due on your 2019 accounts plus the preliminary tax due for 2020. This can be either the tax you paid for 2019 or an estimate of what you owe (if your estimate is less than 90% the actual amount you calculate in 2021 you are liable to a penalty)
Basically in Nov 2020 you will have to pay two years in one go