Did you receive the 1st EIP payment in the same account as you receive your SS benefit payments?  If so, the IRS would have sent the 2nd EIP to the same account and you would have received an IRS Notice 1444-B for the second payment.

The IRS probably denied your Recovery Rebate Credit on the 2020 tax return because they have records showing that you received the payment.

If the payment was never received by you a trace can be put on the payment by the IRS.

See this IRS website - https://www.irs.gov/coronavirus/second-eip-faqs#paymentlost

May 1st EIP was mailed to my ex husband.  I had changed all my info with IRS but all got messed up somehow. Now im still waiting  on 2nd and 3rd pymnts.which I desperately need due to limited income. Getting Farther and farther behind.  I did get notice sayin 2nd pymnt was maiked never got it. Then got notice saying change was made to the recovery rebate to $0 until reviewed. No 3rd pymnt either. I'm in desperate need of this money. To  catch up bills  ive never been behind til now. My ex got everything. 

I don't understand why the 1st PYmnt was NOT directly deposited to my bank account just as my SS is.  why I disnt het the 2nd and 3rd pymnts direct deposit as well. I can't get am amswer from IRS