I was told I would get an e-mail to amend my 2020 return because I got the second stimulus payment after I filed. I have not gotten it. Why?

If you signed up, by February 6 via the TurboTax link, to have your tax return sent back to you, you will receive an email with further instruction per this link. 

I did do that on the 4th. Nothing yet. 

You should receive the email sometime today, February 8, 2021. Be sure to check your spam/junk folder if you don't see it in your inbox. For additional information see: I've already claimed the Recovery Rebate Credit. How can I review and update my 2020 tax return?