If that showed it was accepted (or if you mailed the return), what do you see at the IRS website below for the status of your Federal refund? https://www.irs.gov/Refunds NOTE: When using that tool, use only the Federal refund amount, and not any total refund amount that includes a state refund. The amount to use is on your Federal Form 1040, Line 20a.
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.