Because the IRS issues refunds, not TurboTax, we cannot say for certain why there is a delay.
It generally takes the IRS 21 days to issue refunds. Since it's been more than 21 days since your return was accepted, we suggest contacting the IRS directly to inquire about your refund. Go here for tips on reaching a live IRS agent when you call.
Refer to the following TurboTax FAQ for situations that could delay your refund: What if my IRS refund is taking longer than 21 day ...