Retirement tax questions

Wait really ? So in 2020 i used it with $0 in income because i was on unemployment the whole year. Same thing for this tax season. Why was i able to use the lookback on last years tax return and not this years ? I have $0 in Earned income in 2020 AND in 2021. But last year i was able to claim it and this year im not ? Makes no sense to me. And while i was doing my taxes why wouldnt the system tell me something if it was different this year ?