NJ 1040 not calculating

For some reason, the NJ 1040 shows income on line 27.  It is not pulling anything into line 30 or below until a zero in line 50.   There is only between $1000-$2000 of income.  As a result, the program shows zero tax due.    Why aren't the calculations flowing down?  Is the first X of income in NJ not taxable?