Having this trouble when applying the sum formula

[geminiwwwww20]

Does anyone can help me to solve this prob? 

[#2]

You are using and IF function within a SUM function, which is causing this error. In your formula the function SUM is seeing your IF statement as another number to sum (which isn't).

I see that you have a criteria for SUM. What you need here is SUMIF or SUMIFS.

[#3]

Hi, I’m using =SUM(AA:BB) in the beginning but it showed #VALUE!
So, I press the HELP button, it showed these solution ( refer to the picture above) but it not works.

[#4]

Do you have valid Data in AA to BB?
Try this in place of the formula you are currently using (shown in the picture in cell N2):

SUMIF(M2:M521,"<>ISERROR("&M2:M521&")",M2:M521)

[#5]

@geminiwwwww20 Note that your formula has three apostrophes ( ''' ),

rather than the two quote marks ( "" ) as indicated in the help screen.

That should fix it.