help when i try to place tekkit blocks on my minecraft server it they disappear?

[minecraftexsplore1]

so as u can see from the title when i pick a block from creative and try to place it you see it for 1 sec and then it disappears there are no problems when i start up the server or any thing like that so i dont know what is wrong pls help me  

 

[Curunir]

It's very simple: You are not running a Tekkit server.

In the server package, there are actually two server files: the vanilla server and the Tekkit server. If you start the vanilla server, then of course it will reject all mod-originated blocks because they do not exist. Your world will also have no mod-generated ores whatsoever.

Fix this by running the server correctly. There is a launch script to help you avoid this mistake, called launch.bat (Windows) or launch.sh (Unix/Linux/MacOS).

[minecraftexsplore1]

ok thx  i will try this thank u