Only the IRS controls when and if a Federal tax refund is Approved and Issued.
The dates for receiving a tax refund after it has been accepted by the IRS are only estimates based on the IRS target of issuing a tax refund after 21 days from the date it was accepted by the IRS. This is a target only and not a guarantee.
After the tax return has been Accepted by the IRS (meaning only that they received the return) it will be in the Processing mode until the tax refund has been Approved and then an Issue Date will be available on the IRS website.
See this IRS website for federal tax refund FAQ's - https://www.irs.gov/refunds/tax-season-refund-frequently-asked-questions
Use this TurboTax website to check the status of an e-filed return and if it was either accepted or rejected - https://turbotax.intuit.com/tax-tools/efile-status-lookup/
If accepted by the IRS use the federal tax refund website to check the refund status - https://www.irs.gov/refunds
As you have probably guessed, I too am in need of my refund. Generally, if you check the IRS2go app there are three stages that the return goes through Accepted, Approved, Sent Refund. From my experience, the refund is accepted within 24hrs of signing and submitting. This year (2020) my refund was accepted within hours of submitting it. Now, the last time I got a refund it was APPROVED within 72hrs after it was accepted. However, every year is different. This is why you get the generic "you receive it within 21 after you file". Furthermore, the IRS has released the schedule: if your return is accepted on Jan 27 the direct deposit should be sent on Feb 7.
Hopefully, this helps.