I got a letter on Feb 15th saying in about 7 days I'll get my EIP2 for $600 but never got it, There was no info on the IRS Get My Payment tool. How do it get it?1040-X?

What do I put on the 1040-X to get my second stimulus check, even though I got a letter in the mail saying ill get it and that was on Feb 15th. Thank you for any future advice