Help with SUMIFS

[OTPM]

Hi
I am struggling with a SUMIF formula and need some help.
I am trying to build a Resource Capacity/Availability workbook and what I need to do in the SUMIF formula is as follows:
Total the values in Sheet1 Column I where the Value in Sheet1 Column A is equal to the value in "Skillset Availability" Column A is equal to the value in Sheet1 Column A and the month value in "Skillset Availability" Cell C1 is the same as the month value of each date in Sheet1 Column E.
Hope this makes sense. A sample workbook is attached to show where I have currently arrived at.


Any help would be appreciated.
Tony