Displaying Related Fields from Custom Modules

How can I display related fields from custom modules?

I have a custom module called “Representatives”, and each associated with an Account.

• I have a one to many relationship between Representatives and Accounts.
- From the Representatives modules, I can select the account associated with an opportunity, and this works great.
• I have a Many to Many relationship between Accounts & Opportunities, and I want to be able to see which Account a Representative is associated with from the Opportunities (List View).

However, I cannot seem to find the Representatives > related Account field from Studio > Opportunities > Fields.

Flex Relate seems like it should work, but it isn’t pulling the Accounts data at all. Has anyone gotten something like this to work?