I have an aggregates sales forecast module that only has time dimension.
The sales line item in the aggregation module is doing a lookup at sales metrics module that has stores and scenarios as a dimension.
When the lookup against the stores is the top level item "All Stores" it returns 0. But in sales_metrics screenshot it definitely has data. But when I change the lookup from "All Stores" to just one of the stores in the aggregation module then it works (ignore the fact that the value for the one store below is same as All Stores ... it's just test data)