form 8829 line A in simplified method is $0 - problem

I use simplified method for calculating my deduction for home office use for business.  In the simplified method worksheet, line A is showing $0.  Something is wrong.  I can't believe that the gross income limitation would ever be $0 unless you did not make any money with your business.  In past years, it usually had my gross profit from my 1040. 

 

TT is not allowing me to overwrite that $0 with my gross income from my business.  It also won't allow me to manually enter the $ amount from line F in line 30 of Schedule C.  How can I get my $750 deduction for my business use of home?