Calculate the Earned Income Credit (EIC) for each year using the respective AGI amounts. Select the one AGI amount that gives you a bigger refund or less of an amount due.  

The special look back is for taxpayers who have less earned income in 2020 versus 2019 not for taxpayers who earn more in 2020 than they did in 2019.

• Per IRS: If your earned income was higher in 2019 than in 2020, you can use the 2019 amount to figure your EITC for 2020. This temporary relief is provided through the Taxpayer Certainty and Disaster Tax Relief Act of 2020. 

To access the IRS Taxpayer Certainty and Disaster Tax Relief Act of 2020 EIC special look back provision, see the steps below.

1. Type EIC in the search and select the Jump to.
2. Continue with the onscreen interview until you get to the Do you want to use last year's earned income? screen.
3. Continue with the onscreen interview until complete

To review the EIC requirements, see What are the qualifications for the Earned Income Credit (EIC or EITC)?

I think that you are trying to e-file.  It's just a proofing device of are you who you say you are.  Remember, public access government computers are the last to get updated.  Your smartphone has newer technology base than the gov.

how do i do this or how doi get 2020 agi dont have copy 2020 return

Please follow the instructions here to get the prior year AGI. @Emilpaul42