Did you use Online TurboTax? Did you choose to efile the return? After paying, one has to continue through several additional screens to electronically sign and transmit the return.
After that one should get 2 emails--the first saying the return had been transmitted, followed by a second email saying if the return was accepted or rejected.
Did your efiled return reject? Or was the efile process never completed?
Or did you choose to file by printing and mailing? If so, TurboTax does not mail it for you--you have to do the mailing.
If you used Online TurboTax, log into your Online TurboTax account. At the Tax Home what is showing for the "return status" of your return? If you don't see any "status" on the main Tax Home page, then scroll down and click on "Your Tax Returns & Documents", expand that section and choose tax year 2018, then look for the status. Does it say accepted, rejected, printed, started, ready to mail, or what?