Excel 2013 formula not responding

Please look at this above, I wanted the column G to give the multiplication reference of column D3 to D20 and column F3 to F20 and I have applied the formula but excel 2013 didn't respond to that, I used handle to pull down the cell that has the formula from cell G3 to G20 it resulted to 0 but when I click on each cell I see that the normal formula that supposed to give the multiplication result of the implicated cells is not lost, please click on one of the cells from G3 to G19 and see what I mean

Secondly each time I add a value in C Column (Quantity by ml), I expected it to update automatically in a Column H (Total plus) and I have already created the formula, please click on H3 to see the example of the formula, the automatic update only take place on the Row in yellow color below, please kindly help me out I have passed 3 days and nights looking for a solution but unable to find any, is coursing me a sleepless night, I would be glad if anyone can kindly help me out.
Please download the Excel file and see to understand betterView attachment Ink sells record.xlsx

Why have SUM in the formula? Your formula

=SUM(D3*F3)

The multiplication when one cell contains zero will always return zero. SUM is unnecessary

Putting aside the formula aspect, you are multiplying a quantity by a price to obtain a value. If my sales quantity is 0 then my value will be zero whatever the price ! )