When in a modpack I was making, I got this error for awhile, and I tested it through to find that it is refusing to load when Multipart is installed

fml-client-latest.log

I wonder if you can try using version 347

Forge Multipart
You have to use Version 347 as mentioned above, any other Version, including the usually automatically downloaded ones won’t work, and will throw you a Mod Sorting Error, which in on itself is actually a Forge Bug regarding the "after:*" notation that FMP happens to use.

This is quoted from https://gregtech.overminddl1.com/downloads/gregtech_1.7.10/index.html

I wonder if you can try using version 347

Forge Multipart
You have to use Version 347 as mentioned above, any other Version, including the usually automatically downloaded ones won’t work, and will throw you a Mod Sorting Error, which in on itself is actually a Forge Bug regarding the "after:*" notation that FMP happens to use.

This is quoted from https://gregtech.overminddl1.com/downloads/gregtech_1.7.10/index.html

I'll try that once I get my pc set up again, I'll let you know if it works or not

I wonder if you can try using version 347

Forge Multipart
You have to use Version 347 as mentioned above, any other Version, including the usually automatically downloaded ones won’t work, and will throw you a Mod Sorting Error, which in on itself is actually a Forge Bug regarding the "after:*" notation that FMP happens to use.

This is quoted from https://gregtech.overminddl1.com/downloads/gregtech_1.7.10/index.html

yep that did the trick