Won opportunity is not showing up in ROI figures on the Campaign

Good day all.

So, I have a Campaign and an Opportunity that is linked to the Campaign. The Opportunity is 100% won with an amount ($) yet that amount is not showing up nor being tallied up in the Campaign header under "View ROI":

I would assume that there should be 1 there. So, any ideas what is causing?

Am I just not doing some crucial configuring or ?

Thanks guys,

KGM