Recipe not bringing over agg values in a join

From recipe #1 I have a dataset #1, just a normal object related dataset, of account and opportunity. The opportunity has a text field in it which is a unique ID (X)

I also have recipe #2, which has one dataset from an external SQL server, it has many lines of X with different volume and prices. It is aggregated by X, so that we get sum of vol and sum of prices.

Both datasets on their own all good, but when I try to add dataset 2 to dataset 1 in recipe #1, with X as the key, they match up alright but the aggregated values all come over as 0?

Is there something basic im missing?