Did you start a server with mods installed and none of them are working or loading? There are two things you need to check.

Using correct server jar

A common mistake a lot of people making creating Forge servers for the first time is attempting to run the server using the minecraft_server.jar instead of the Forge server jar.

Correctly install mods

Make sure that the mod is correctly installed in the mods/ folder and you’ve downloaded our mods from a genuine source and not a third reposting site. You can find our mods officially on CurseForge.