So, it seems like Chisel isn't being loaded on the server but the client is fine. I can tell this because when I go to craft a chisel I can't take the output from the crafting bench and its called "Unnamed 0". Nothing from chisel shows up in JEI either. (In singleplayer, it works fine)

Forge: 2281
Chisel: 0.0.11.25
ConnectedTexturesMod: 0.1.0.13

Please post the startup log from your server.

Here you go: Here (apologies, pastebin has a character limit...)
From what I can see, these lines:

"Unable to read the jar file Chisel-MC1.10.2-0.0.11.25.jar - ignoring"
"java.util.zip.ZipException: error in opening zip file"

Are what is affecting it. Although this is happening with Decocraft a bit further down as well.

A bit further down also:

"Zip file Chisel-MC1.10.2-0.0.11.25.jar failed to read properly, it will be ignored"
"java.util.zip.ZipException: error in opening zip file"

Which seems to be affected by the first bit.

Sounds like some of your jar files, including Chisel, got corrupted at some point. I would try downloading them again.