Here are two situations that might produce the behavior you are seeing. There might be others as well. In these cases, the software is working correctly, but you have a tax situation on Schedule C that prevents you from benefiting from additional business expenses.
(1) You are claiming expenses for business use of your home on Schedule C line 30. On Schedule C, line 29 is positive (a profit), and line 30 is equal to line 29, so line 31 is zero. If you add expenses that are less than the tentative profit on line 29, line 31 remains zero and your refund does not increase. The deduction for business use of your home cannot create a loss. The deduction is limited to the amount of your tentative profit, so reducing the tentative profit by entering more expenses reduces the business use of your home by the same amount. For example, entering $289 for advertising reduces the business use of your home by $289, so your net profit remains the same and your refund doesn't change.
(2) Schedule C line 29 is negative (a loss), and box 32b is checked on Schedule C line 32. The loss that you can claim is limited, so adding more expenses does not increase your loss and does not increase your refund.
