cant make tekkit items on techinc launcher

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a few weeks ago i made a muliplayer server for my friend and i to play on. i wanted a mod that would work so i looked up techinc and found techinc launcher downloaded it and told my friend to download it and he did after going on our server we found out that we cant make tekkit items only normal items. my friend thinks that if i make a new server it will help but i dont think it will so what can i do to have this working BTW we were playing on the server before we got techinc