What does this error mean "Box 20 Code Z has been selected but no Section 199A income has been entered on Statement A"?

I have followed all the suggestions in correcting this error in Turbo Tax and nothing works! Very frustrating and I have been using TurboTax for over 10 years.  Last year we have Schedule K-1, but no error was generated when leaving Box 20 blank.  This year it is different, preventing me to e-file my tax returns.  Frank Chen.