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.
Ink sells record.xlsxInk sells record.xlsx

Your problem is that in column D you do not have data. It's blank, which excel reads as a zero. You will not get anything for g if you don't have a value in d. Same with row f. When updating column c, if there is no value in F, excel will read it as a 0 and nothing will update unless there's values in both the c and f columns.

I am so grateful really with you kindly concern liz5818, do you know what happen that confused me, you see when I inserted data in the Cell the update didn’t take effect instantly within the resulting Cells rather when I click to register the file it is at that time the update changes took effect, which as my knowledge with little experience that I have with Excel it is unusual, I don’t know if I am wrong by using the word unusual for excel here.
The above clearance/explanation is based on the Cells that I have data in it, and you are perfectly right when you say that I will not have any response from excel in a Cell where I don’t have any data in it.

But if the confusion of late recognizing data input and updating late not until clicking register did not occur the question of not updating empty Cell wouldn’t have being my problem at all, I should have known the reason.
But it is the Cells where I have data in column C and column D brought the confusion because excel updated the reference Cells late, just on registering, once again thank you for kindly concern.

Sampson Jerry

Please is there any way to solve this problem of this late updating of excel that I am experiencing now, is it normal? When I inter data it will remain like that until I click on register then it will update in the referencing cells, this is dangerous because if I have to go far in interring lots of data I might not be able to find out errors if there are any.

Yes I just did as you directed and it worked perfectly, thank you all.