Ok so I recently made a mob farm on a Hard-core PvP Factions server. The owner said mob farms are fine and there is nothing that is against them in the rules. Just as long as you don't cheat to get the materials to make it. So I made a 4 layer mob farm. The first layer being STONE BRICKS, the 2nd, 3rd, and 4th layer, being made entirely out of COBBLESTONE. I have done this design on multiple servers and they all went fine. But on this server, I'm facing difficulty in getting HOSTILE mobs to spawn within the farm. They do not spawn when I'm near or away from the farm. This farm consists of 7x7 Squares with a 3 block gap water canal that will bring mobs down the center. The center is a chute that is a 3x3 square that descends all the way down the mob farm and leads to the a water stream that flows 8 blocks (the max length water may flow in) to the killing chamber. There is a collection pit that consists of a one block deep water canal that leads drops around the killing chamber. I have had numerous friends of mine come on and take a look, even the server owner, and they all said they were stumped. Can someone please come onto the server that and take a look at it and see if YOU know the problem? I will send the IP to you in a PM. Thanks!
PS: This entire farm is based off of natural dark mob spawn. There are NO SPAWNERS. It is entirely based off of natural darkness mob spawn patterns!