I have a server and was playing with other players tonight. We've noticed that they are unable to access Warehouse Interfaces and Tree Farms. Is there something I need to do?

Interestingly, they can go directly to the Warehouse Storage blocks and can see inventory, but they can't do it through the Warehouse Interface.

Anyone else having this problem? It's really stifled the ability to have multiple players in this world.

Note: I've set spawn-protection=0 and it still doesn't work. None of the players on the server (myself included) are OPs.

Well, this case it turns out that I needed to RTFM: looks like Ancient Warfare uses scoreboard: I had never heard of it.

scoreboard teams add <name>
scoreboard teams join <team> <player>
scoreboard teams join <team> <player2>

And now it works.

Sorry for the trouble but hope this helps someone else.