If your return was accepted 21 days ago (excluding holidays) or more and you have not received an update via the Where's My Refund tool, you can follow the instructions in the following FAQ to contact the IRS for further assistance.
https://ttlc.intuit.com/community/refund-status/help/what-if-my-irs-refund-is-taking-longer-than-21-days/00/26080