Hello, the AGI transfers over automatically for all returning TurboTax Online users. It's best to make sure you're in the same account as last year, even if you already started in a different account this year. Here's the account recovery tool to find any other accounts you may have: https://myturbotax.intuit.com/account-recovery/
If that's not it, did you amend the return by chance? If you did, try using the original AGI amount that was transmitted to the IRS.
I'm also posting an article below that helps confirm the AGI location to make sure you have the right amount, just in case:
https://ttlc.intuit.com/replies/3301618