Summary field not working--suspect key and reference field issue

The issue is that every month a new Forecast is generated for each Project Number.  So a given Project Number will have numerous Forecasts.  This is done this way so we can go back and look at how much was forecast for, say, June during previous Forecasts and we can see how things change.

I realized this makes Project Forecasts to Project Tasks a many-to-many and I went down that rabbit hole for a while but thought this would be simpler (if it would ever work).