Why can't I change the difficulty?

[Natebobate]

The difficulty of the server is on easy but I want it on hard. I've gone to the server settings and changed it from easy to hard and restarted it but it is still easy in-game. I thought that maybe it still appeared as easy in-game but was actually on hard mode so to test this I changed it to peaceful, restarted it, aaannnnd.... there were still mobs.

[_Tarna_]

In game, try doing the command /difficulty <mode> so like /difficulty hard and see if that works.