Was your return Accepted? When you efile you get back 2 emails. The first email only confirms the transmission. The second email says if the IRS (or state) Accepted or Rejected your efile. Just paying the fee doesn't file the return. After you paid did you continue on to the very end and hit the big orange Transmit Returns Now button?
When you log into your account you should see the status and if it was Accepted or Rejected, Started, Printed, Ready to Mail, etc. what does it say?
Since it was rejected it never got filed. You should have got a reject email saying why.
You now have to print and mail prior year returns. When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s. Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS or State received the return. Mail federal and state in separate envelopes.
You need to register a 2019 online account to access prior years
Depending on the reason it rejected you may need to fix something. How to finish a prior year online return
We also received a letter. They got our payment owed, but did not receive our file. Our account when we log in for 2018 says filed.
If the IRS is requesting a 2018 tax return -
To access your current or prior year tax returns sign onto the TurboTax website with the userID you used to create the account - https://myturbotax.intuit.com/
Scroll down to the bottom of the screen and on the section Your tax returns & documents click on Show. Click on the Year and Click on Download/print return (PDF)
A 2018 tax return can only be printed and mailed, it cannot be e-filed.
Print, sign, date and mail the tax return to the IRS. Include with the mailed return any forms W-2 and 1099 which have taxes withheld. Go to this IRS website for mailing addresses - https://www.irs.gov/filing/where-to-file-paper-tax-returns-with-or-without-a-payment
See this TurboTax support FAQ for accessing prior year online tax returns - https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-access-my-prior-year-return/01/270...