Concat & Filter from second data source won't show multiple records

[misc]

My app needs to share a report with different stakeholders depending on the type of report it is. I have configured a combo box which both autopopulates with these stakeholder groups and can be updated manually by the user if need be.

I have edited this post heavily as I managed to answer my original question on lookup fields, however I'm still encountering the same issue as I was previously, despite a different formula.

Data source 1 is called Incidents, it is the data source for the form

Data source 2 is called Mailing Lists, it is linked to Data Source 1 through a Lookup field, shown on the form as a combobox selection of its column 'Report'. 

I want to create a string of the email addresses by making it match the Mailing list chosen in the combobox to that in the 'Mailing Lists' data source. The formula I have at the moment only shows the first record which matches from the 'Mailing Lists' source, rather than searching each record against each choice made and putting these together in a string.

Eg. ComboBox has Option 1 and Option 2 selected, the app recognises that Option 1 equates to Red on the Mailing List data source and provides all the data from the 'Email addresses' column, then continues searching and recognises that Option 2 equates to Black, and provides all the data from that record's 'Email addresses' column, both separated by "; ".

At the moment, it only returns Red and stops looking.

Any help is really appreciated on this one.