I've tried several variations, but can't seem to recall, or work out how to use SUMIFS properly

I want a formula that will show the total sum of figures per person per specific time period (i.e. month), but am getting nowhere. i can create separate formulas to get the answer, but would rather do it in one - can someone explain where i'm going wrong?

My best effort looks like this:

=SUMIFS(Data!H2:H10,'Front Page'!A10,Data!G2:G10,Data!$M$2:$M$10,">="&DATE(2018,8,1),Data!$M$2:$M$10,"<="&DATE(2018,8,31))

which i'm sure you can see is coming up with VALUE?

any advice greatly appreciated