If you efiled, you can double-check that it was successfully efiled and accepted here:
The IRS releases most refunds within 21 calendar days after the e-file has been accepted (received), not 21 days from the e-filing date. For mailed returns, allow 5-6 weeks from the postmark date.
Wait 24 hours after your federal return has been accepted before looking it up at Where's My Refund? See also Where's My Refund FAQs.