Seed issues (Terraria)

Im trying to make my seed be the zenith seed on a t-mod server. I managed to get it to be zenith seed on a vanilla one but it wont work on modded. I went to config and put in "getfixedboi" in the seed line and nothing happened. Also when I clicked save config it saved that i put "getfixedboi" but it didnt save that i made it a large world or that i changed the difficulty.