Download-hearts-of-iron-4-field-marshal-edition-v1-9-1-online Page

This sounds like you are looking for a specific, older version of the (v1.9.1) to play online.

To play online with others on this specific version, everyone in the lobby must have the same "checksum" (the version code). Right-click in your Steam library. Select Properties > Betas . This sounds like you are looking for a

Are you trying to run a specific that only works on version 1.9.1? This sounds like you are looking for a

Click "Multiplayer" in the main menu. You can use the Steam "Invite Friend" feature or the Server Browser. This sounds like you are looking for a

The Field Marshal Edition features are tied to your account's DLC list. Ensure the launcher shows version 1.9.1.