You'll need to add Form 8862: Information To Claim Earned Income Credit After Disallowance to your return.
In the Earned Income Credit section when you see Do any of these uncommon situations apply? Check the 4th box, I got a letter/notice from the IRS telling me to fill out an 8862 form to claim the Earned Income Credit. Here's how: https://ttlc.intuit.com/replies/6138577
