The error message you are seeing on the wash sale entries is a result of automatic rounding. If the wash sale adjustment is $0.49 or less, then it is automatically rounded to zero. This type of rounding is allowed by the IRS.
Unfortunately, zero is not a valid value for this field for TurboTax, thus the error message.
To enter a disallowed Wash sale:
Income & Expenses
Note: You'll need TurboTax Premier, TurboTax Live Premier, or TurboTax Self-Employed, TurboTax Live Self-Employed, to add any 1099-B forms.
I received the reply but later went on to work on state taxes and when I finished and looked at review again, the message was that everything was ready to submit even though I had done nothing with the wash sale issue. I've not had time to work on taxes since then but this is confusing to say the least.