Check the Where's my Refund tool or use the IRS2go app. If your filing isn't showing as received or accepted, that's why. You should receive an email telling you that it was accepted by the IRS if it's gotten to that stage yet. Otherwise, TurboTax gives a window of "typically up to 48 hours after" the return is accepted; if you still haven't gotten word after that, I'd call them.
I received mine after 40 hours, so best of luck.
