Retirement tax questions

Hi - having a somewhat similar issue. In Jan 2022, I deposited $6000 of POST TAX dollars into an IRA, and then immediately converted it to a ROTH IRA account (all on Charles Schwab). I thought that this contribution and rollover would count towards my 2021 tax year. Since I did all of this in Jan 2022, Schwab will not send me any tax documents until Jan 2023, so I have manually entered in 1099R information on TurboTax. I did the following: 

Box 1 Gross Distribution: $6000

Box 2a Taxable Amount: $0

Box 2b:
CHECK: Taxable amount not determined box is checked

CHECKED: Total distribution is checked

Box 7 Distribution Code: 2

CHECKED: IRA/SEP/SIMPLE box is checked

 

This approach gets form 1040, Line 4a to show $6000 and Line 4b to show $0 as the taxable amount - which is correct. HOWEVER, when going through the final review, TurboTax says that on the 1099R, the Taxable Amount Cannot be ZERO if there is no prior year excess traditional IRA contribution on line 4 of the IRA info worksheet.

 

I don't know what this means, and I am really at a loss as what to do. This should be a fairly simple backdoor roth conversion. Please help if you can. Thank you!