Why does my account say I have already submitted a copy with my social security number. I haven't. I do have another account email but it hasn't been used since 2016. Did someone else file my taxes?

Did you do anything for your stimulus check on the non-filer site?  If so, that will cause you a rejection if you are now trying to e-file a tax return.

Or if someone claimed you as a dependent, you will not be able to e-file.

When your tax return is rejected for a duplicate SSN, you will not be able to e-file.  The only way you can file is to print, sign and mail it.  And sadly, expect a long processing delay for a mailed return.

What is the rejection code and message for the rejected tax return?

Did you use the IRS website for non-filers to register for the stimulus?  If so, then you filed a 2019 tax return with the IRS.

See this TurboTax support FAQ for the procedure to use when the non-filers website was used to register for the stimulus and you are now filing a 2019 tax return - https://ttlc.intuit.com/community/tax-topics/help/stimulus-how-to-file-your-return-after-getting-reject-r0000-902-01/01/1602609