when I start Minecraft it crashes with this message:

Error: net.minecraftforge.fml.common.LoaderExceptionModCrash: Caught exception from Modular ForceField System (modularforcefieldsystem).

I came here for the same error on the 1.10 version, the logs indicated that MFFS was looking for the guide-api:
Caused by: java.lang.NoClassDefFoundError: amerifrance/guideapi/api/impl/abstraction/CategoryAbstract

Installing the mod fixed the crashes:
https://minecraft.curseforge.com/projects/guide-api/files/2325317

That text is shown on every error, so it may not be the guide book text, I am glad your error was fixed though, I am sorry I may have forgot to mark it as needed in curse

Can you post the log, please?

Hey, so I'm trying to launch the 1.12.2 version of MFFS. I added the updated versions of Guide-API, Industrialcraft, EnderIO, and EnderCore. I tested with various versions of each of the mods but it has crashed every time. Is there something that I am missing? I'm using MultiMC to try and launch them with forge.

Here is my crash report :)
crash-2018-07-22_00.25.31-client.txt