SUMIFS Not Returning Correct Value

Hi All,

I've been having some issues with a specific SUMIFS Formula that I'm trying. I've attached a worksheet with the data format I'm using - I've replaced the data with a flat nonsensical 1234 to alleviate office privacy concerns.

I'd have thought that the following should return the value for May 2015's Booked, Gross, AUD total sales:

=SUMIFS(S:S,A:A,Booked,B:B,Gross,C:C,AUD,D:D,May,E:E,2015)

Instead I'm only getting a "0" value and can't understand why. I know this is a simple one for me to work out manually but I'm trying to crack the formula to automate a recurring report where the variables will change.

This is my first post, apologies if the rules aren't adhered to 100% or if it's hard to follow - please let me know how I can correct this if so.

Thanks!