Spotlight Search is not working on our server environment

I have a dedicated Mac Pro Server running Server 5.1 software. Whether searching from the server desktop or from any of the networked users, Spotlight search is not searching the volumes. Seems to have been an issue since we upgraded to ElCap and the latest version of Server. What have I missed. FYI, I am NOT an IT guru, but fancy myself a DIYer. Any guidance would be greatly appreciated.

El Captain 10,11.4

Mac Pro Server (Mid 2010)

Server 5.1