Hello, the AGI transfers over automatically for all returning TurboTax Online users. It is also located in the Timeline section of the account that E-filed the return. Look under 'View Adjusted Gross Income'.
If there are issues with it being located or accepted, I would check and make sure you're in the same account as last year. Here's the account recovery tool to find any other accounts you may have through alternate methods. Just be sure to log out of any open tabs before starting the process: https://myturbotax.intuit.com/account-recovery/
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
