Having trouble adding Sugar Connect to desktop Outlook

We have just deployed Sugar Connect for a client of ours and while this works perfectly in the Outlook Online Webmail version, none of the users and see Connect in the Desktop version of Outlook (despite it being a supported version).

They have an E3 subscription which is Enterprise Grade (assuming?). We think there could be a security setting blocking it from being deployed.
But we've been through the portal and could not spot anything.

Has anyone experienced this frustration with Connect?

Thanks a bunch <3