First be sure your 2018 return was successfully filed. Log in and in the left menu column click on Previous Taxes then choose 2018. Or you can also get there from the Tax Home page by scrolling down to "Your Tax Returns & Documents" and expand that section.
When you choose 2018, does it say it was filed, and if so, what is shown for the "status"? Does it say accepted, rejected, printed, started, ready to mail, or what?
If the status shows that it was accepted by the IRS, or if you printed and mailed the return but never received the refund, we can tell you how to phone the IRS to speak to a live agent.
Also, if it shows "accepted" but you never received the refund, how did you pay the TurboTax fees that year? Did you pay upfront with credit/debit card, or did you choose to pay the fees out of your Federal refund?
