Problem with calculating a cell across different sheets.

[elmendaratata]

As you can see in the first image, I want to calculate the average of cells B2:G11. For this, I've used the following formula:

=AVERAGE('Argentona - Mataró:Sese 2'!C2)

But then I realized that there are still some Excel sheets missing data for some months. So, I want to calculate the average with a condition: Calculate the average ONLY if there is a +0 value below. Example:

In this case, calculate B7 if B20 (because its 15-Aimat) has a 1. If it has nothing, then don't calculate.

In other words, calculate the average of B2 from the pages where B15 is >0. I say >0, because sometimes its no 1, it's 0,8, so it's important to include everithing that is not 0, not only the 1.
To do this, I wrote the following formula:

=AVERAGE.IF('Argentona - Mataró:Sese 2'!B15, ">0", 'Argentona - Mataró:Sese 2'!B2)

Since it didn't work, I changed and used this:

=AVERAGE(IF('Argentona - Mataró:Sese 2'!B15>0, 'Argentona - Mataró:Sese 2'!B2))

Then this:

=AVERAGEIFS('Argentona - Mataró:Sese 2'!B15, ">0", 'Argentona - Mataró:Sese 2'!B2)

But it continued to give me #VALUE!. I tried one last option:

=SUMIFS('Argentona - Mataró:Sese 2'!B15, ">0", 'Argentona - Mataró:Sese 2'!B2) / COUNTIFS('Argentona - Mataró:Sese 2'!B15, ">0")

But it still shows #VALUE!. Can anyone please help me? What's wrong?

I've attached images of the other sheets for reference:

 

[arthurbr]

AVERAGEIF does not work with a 3D reference
Perhaps have a look at averageif across worksheets [SOLVED]