I received a letter from the IRS that my 2019 taxes were not filed, but I thought they were completed on TurboTax? How do i look into this and solve?

The IRS just published and released this statement.  It likely applies in your situation.

IRS Statement about CP59 notices | Internal Revenue Service

Insanity!  Thank you for the response.  I don't feel completely comfortable counting on the error to be corrected even though it says to disregard the letter. Is there any action I can take to verify that the IRS has received my return?

If you e-filed using TurboTax, you should have received an "Accepted" email from them after filing.  I think that's pretty much all the confirmation you'll get, but it's reliable.  Or you could try to call the IRS, but I'd be surprised if you could even speak with anyone.  This COVID mess has really slowed them down.