If you are seeing a message that your return is "Ready to Mail", you must print and mail the return yourself. TurboTax does not mail returns for users. See the instructions below to go ahead and print your return for mailing to the IRS.
https://ttlc.intuit.com/replies/3401713
*** I am NOT a tax expert. I am a seasoned TurboTax user, and volunteer to provide assistance to TT users. Nothing I post is to be considered TAX ADVICE; I bear no legal liability for responses.***