I'm running Minecraft Forge on 1.12.2 to use some mods on my server with some friends. I installed Forge 1.12.2 on Client and Server, and I opened the forge jar file in my server folder using batch file, and it created the mod folder. I proceeded to drop in my mods into the mod folder on my server and also the mod folder in client Minecraft (.minecraft). When I start the server, I can join fine, I can clearly see the mods showing up, and they are visible in creative. However, when I want to actually use the mods, they don't function as should. For example, I wanted to use the Modern Warfare mod. I can select a gun, I can have it show up in my hand, but it refuses to do anything when I try an action. This is the opposite case for when I play the mods in singleplayer, as they work perfectly in singleplayer. Another example being in ProjectE, I will select a block, place it down, and it will vanish. The opposite for singleplayer.
Mods (Selected Version for 1.12.2):
Modern Warfare, General Disasters, Tails Mod, JourneyMap, ProjectE, and Erebus.
Alright, so apparently I was starting the server incorrectly. I was starting the Minecraft 1.12.2 server jar instead of the universal forge. It's weird though because every time I had watched a tutorial and a potential fix video they had always launched the server up in the traditional 1.12.2 jar file. My problem is fixed though, thanks anyways.