This year it seems to be taking much longer for returns to get processed. There's no way of knowing exactly when the IRS will update. Some returns may take more time for the IRS to review. You will need to keep checking the Where’s My Federal Refund? tool for updates. Updates are made daily, usually overnight.
However, since your return was accepted 21 days ago or more, you can follow the instructions in the following FAQ to contact the IRS for further assistance.