Paying does not file your tax return - you must then use the big "transmit" button AND then get an e-mail saying that the return was transmitted.  THEN  wait 24-48 hours for another email that tell you then the return was accepted only then did you file.   If you receive an e-mail that rejects the  you must fix the problem and refile.    If you did not receive any email then you did not file at all.

And.....if your 2018 return was not filed. then you need to print it, sign it and mail it now.  It is too late to e-file.

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 and/or your state received the return.

Did the IRS say you didn't file or didn't pay the tax due?

When did you efile?  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?

Maybe it Rejected.  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?

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

https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-access-my-prior-year-return/01/270...

Depending on the reason it rejected you may need to fix something.  How to finish a prior year online return

https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-finish-a-prior-year-return-that-i-...