Ready to mail indicates that the state tax return has not been e-filed. You must print, sign, date and mail the tax return to the state to file the return.
Or you can see if the state tax return can be e-filed using the procedure in this TurboTax support FAQ - https://ttlc.intuit.com/community/e-file/help/how-do-i-e-file-my-state-after-i-already-filed-my-fede...
You complete your tax return by finishing all 3 Steps in the File section. In Step 3, to e-file your tax return, you must click on the large Orange button labeled "Transmit my returns now".
After completing the File section and e-filing your tax return you will receive two emails from TurboTax. The first email when your tax return was transmitted and the second email when the tax return has either been accepted or rejected.