I completed and paid to prepare my 2019 tax return using TurboTax. Apparently it was never filed. I cannot find an option to efile the return. Is it possible to do so?

No.  E-filing has been closed permanently for 2019 returns since October .   The only way to file it is to print it, sign it in ink and mail it.

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/state received the return.

Federal and state returns must be in separate envelopes and they are mailed to different addresses.  Read the mailing instructions that print with your tax return carefully so you mail them to the right addresses.

https://www.irs.gov/filing/where-to-file-paper-tax-returns-with-or-without-a-payment