Attention: You most likely received this IRS rejection because you filed a Stimulus, Simple or Non-Filer Return in 2020. If you did, the IRS considers this to be your regular 2019 Tax Return, thus your regular 2019 return is resulting in a rejection. Did IRS did not communicate this with taxpayers and for many taxpayers the only option now is to prepare and file a tax amendment.
Here are the instructions on how to prepare an IRS tax amendment or Form 1040-X on eFile.com: https://www.efile.com/tax-amendment-form-1040-x/
Note: When you prepare and eFile your IRS and State Return and they get rejected your State Return is under "My Account". Download, print, sign it and mail it in. Find the mailing address here: https://www.efile.com/states/
Problem: The IRS has rejected your return - not eFile.com - because the return primary SSN or Taxpayer Identification Number (TIN) has already been used on a filed return with the IRS. If applicable, this might also apply to your state tax return.
Solution: Let us help you turn this into an IRS acceptance. Sign into your eFile.com account: https://mytaxes.efile.com/1040/SignIn/, and click Name and Address on the left side menu. Scroll down and make the necessary correction of updating your and/or Dependent's SSN or TIN. Save the changes, click Continue and follow the screen instruction to re-efile your federal and state returns for free. You can do this as often as it takes to get accepted. However, should you have entered your SSN and/or TIN correctly and you keep getting rejected for any reasons, PRINT your return(s) - IRS and State(s) - and MAIL it in on time here: https://www.efile.com/where-to-mail-tax-return-form-irs-mailing-address-for-refund/
After that, contact the IRS at 1-800-829-1040 and/or State and discuss your tax return in more detail. If the IRS does not accept your return, because a return under your SSN has been accepted by the IRS ask yourself if you have already filed elsewhere or if you have data security concerns please visit: https://www.efile.com/tax-return-identity-theft-and-refund-fraud/ . If you have already filed a return and are trying to change or correct it, please visit https://www.efile.com/tax-amendment/. Contact us with further questions or assistance at https://www.efile.com/tax-service/contact/efile-contact/.