Refunds are issued by the government, not TurboTax. Therefore, we can't say for certain why you haven't received your refund.
Check the IRS Where's My Refund? site to see if your refund was approved and if there is an estimated deposit date listed.
It generally takes the IRS 21 days to issue refunds. If 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 tax situations that can delay refunds: What if my IRS refund is taking longer than 21 day ...