Federation tests OK but fails to work

Description

I have 3 x Rocket chat servers within our company network servicing 3 different divisions of the business. There are 3 due to them each requiring different branding and integrations etc.
We would like to implement federation so that we can communicate across the 3 servers.
I have implemented federation using DNS and the federation test button comes back successful for each server however when trying to search for a user on a different server returns no results.

Each server uses a different domain name.
All servers are using the same active directory for authentication so anyone can login to any server.
The servers are behind an nginx reverse proxy which handles SSL handshake on port 443 and certificates and forwards to non-SSL ports (80 or 3000).

Has anyone had any success setting up federation in a similar environment and can offer some tips suggestions as to where this is failing?

Thanks

Server Setup Information

  • Version of Rocket.Chat Server: 2.11
  • Operating System: Linux (Debian 9)
  • Deployment Method: SNAP
  • Number of Running Instances: 1
  • DB Replicaset Oplog:
  • NodeJS Version: 8.15.1
  • MongoDB Version: 3.6.14
  • Proxy: nginx
  • Firewalls involved: pfSense

Any additional Information