There has been a change by the IRS starting with the 2020 tax returns that will reject any return filed with a negative number reported in the proceeds or cost basis fields for Schedule D.
TurboTax is flagging these situations ahead of time before the return is filed in order to prevent the IRS rejection.
Some brokers are still using the old convention for reporting negative values and have not updated their reports to match the IRS.
The error message reported by TurboTax is telling you that the number entered cannot be negative.
Gains from expired options are reported by entering the gain amount in the proceeds column and no amount in the cost basis column. The end result here would be positive.
Losses from expired options are reported by entering the loss amount in the cost basis column and no amount in the proceeds column. The end result here would be negative.
No negative numbers should be entered in either the cost basis or proceeds fields.
If negative numbers have been imported through your brokerage statement, you will need to edit the entries to make the correction.
For additional information refer to the following link:
Sales Price not between upper & lower limits
