Very common. The IRS and state (if applicable) have to release the refunds first. We can tell you some things to check:
About how long has it been since you filed?
If you efiled, double-check with this tool to be sure the return was efiled successfully and accepted:
https://shop.turbotax.intuit.com/efile/efile_status_lookup.jsp
If that confirmed it was accepted, what do you see at the IRS website below for the status of your Federal refund?
https://www.irs.gov/Refunds
If that IRS tool shows that the refund has been sent, report back for more info.
If the IRS tool says it is still "being processed", and if it's been longer than 21 days, we can tell you how to speak to a live agent at the IRS to see if they can tell you anything about the delay.
To track a state refund:
https://ttlc.intuit.com/questions/1899433-how-do-i-track-my-state-refund