I still didn't receive my 2020 tax refund. I've received a letter on September that indicates I have mistakes on my tax return and I'll receive refund in 6-8 weeks.

TurboTax does not get any information at all from the IRS after you file your tax return.  No one at TurboTax knows what the IRS is doing with your return.

The IRS refund site is not showing information now for 2020 refunds.  It is only showing 2021 refund information, so if you try to track a 2020 refund it will tell you there is no information.

To call the IRS:IRS:  800-829-1040  hours 7 AM - 7 PM local time Mon-Fri

Listen to each menu before making the selection.

First choose your language. Press 1 for English.

Then do NOT choose the first choice re: "Refund", or it will send you to an automated phone line.

Instead, press 2 for "personal income tax".

Then press 1 for "form, tax history, or payment".  

Then press 3 "for all other questions."

Then press 2 "for all other questions."  It should then transfer you to an agent.