What does number 9021 on IRS site mean?

Once your federal return has been accepted by the IRS, only the IRS has any control. TurboTax does not receive any updates from the IRS. Your ONLY source of information about your refund now is the IRS.

9021– Reference Code for all math error conditions.

Note that a "math error" can occur if you make a data entry mistake, or forget to claim some income; and thus the refund amount is incorrectly calculated. They will not notify TurboTax about the reasons.

You may need to call the IRS for assistance. 

• Calling is extremely time consuming right now. If you want to try, call very early or very late based on the times below.
  • January - April  800-829-1040
    • Customer service representatives are available Monday through Friday, 7 a.m. to 7 p.m. local time, unless otherwise noted.
    • Telephone service wait times can average 15 minutes. Some telephone service lines may have longer wait times. 
    • Telephone service wait times are higher on Monday and Tuesday
• You can try to Contact the Local IRS Office using this link.
• Final Action if no results: Contact the Taxpayer Advocate Service (TAS). 
  • Select Contact Us, then select to download and complete Form 911, Request for TAS Assistance
  • If you have not opened a case with TAS, call 877-777-4778 
  • TAS is an independent organization within the IRS. Our job is to ensure that every taxpayer is treated fairly and that you know and understand your rights