hi,

see suppose you passed your 12th exam on 2016, then you are eligible to give jee main exam on 2018 and 2019.

from your question I make out that you have passed 12th on 2018, so thats why you are not eligible to give jee advanced on 2020. because your all attempts has cleared.

now see its not like that you can not be a good engineer if you dont get iits, see there is many students who have passed engineering from a tier 3 college, but because of their hard works they are now placed in tier 1 mnc companies.

so if you are interested in engineering give your best shot this time and join some good reputed institute by jee main score. you should know that jee main can be attempts by only 3 times.