If you chose to have your fees deducted from your refund, that may be a cause. Or the IRS may have made adjustments before sending the refund. If the IRS made adjustments you will receive a notice in the mail in a few weeks.
In the meantime, you can contact the IRS for further information.
Contact an IRS customer service representative to correct any agency errors by calling 800-829-1040
TurboTax does not issue refunds and cannot provide any details once the return has been accepted by the IRS.