DaemonUmbra

Oh dear... a log is not a file that is needed to run a program unless it is a program specifically designed to read logs (to put them in a more eye-pleasing format, for instance). Logs are created as records of what a program does, including problems it encounters along the way, therefore a program won't "come with it" and if it does then the log included would be a useless one as it was most likely not generated by an identical setup. How did you install Forge and not have an installer log?

This is intentional! The files are supposed to already be there if you use the Forge installer, if they are not there and the launcher is trying to download them then either you did not run the installer or something went wrong. This is why I am asking for the installer log, it will have the name [name of installer].log, it is generated when you run the installer and will be in the same folder as the installer unless you deleted it.

Yes but please don't necro old threads (I split your reply into its own thread). While the new launcher is a little bit less straightforward you can still change the version that a profile uses relatively easily. Step by step images are in the spoiler because they are large.

The task is setupDecompWorkspace, not just decompWorkspace

I'm getting off track with this, do you have the installer log? The one that the Forge installer creates.

Do you have a logs folder in your .minecraft folder? I am not asking for the launcher log, I am asking for debug.log or latest.log Ok so it doesn't even get to the point where the client takes over... I get it now

This is all moot, Forge for 1.13 isn't out yet. For the record, to my knowledge the error that the Minecraft Client can't download the Forge jar is intentional, the Forge jar should only come from the Forge installer.

You are trying to run 1.12.2 Techguns on Minecraft 1.12.1 Given that you are new to modded minecraft I would like you to take a look at the thread I've linked here, both me and another mod gave our comments to another person new to the world of modded minecraft.

Can you post the installer log?

It might be cfm.cfg, since the undescriptive "cfm" is unfortunately what he uses as the Mod ID.

Do not use 9Minecraft for Mods, see the StopModReposts project to learn why.

MrCrayfish's Furniture mod is trying to use Client-Only code on the server side. This has been fixed on the GitHub but hasn't been fixed in a release yet, I believe the workaround is to disable the welcome message in the mod's config file.

What steps did you follow setting up the mods for this instance, go through what installers you used, the order you used them in, and the options you chose in each one.

Remove NotEnoughIDs, according to Lex this mod has been confirmed to muck up network handshakes, which is what is happening here.

Do you have the installer log?

Can I just have you confirm where you are getting Forge from? The specific URL please.

Did you delete Forge from your versions folder before re-running the installer?

Can you give the URL for "the forge website"? and I mean a URL to the download page, not "this site".

debug.log should be in your logs folder, as described in my signature.

1.7.10 is no longer supported on the forums due to its age. Please update to a Modern version of Minecraft to receive support.

What launcher are you using?

To make a Gist yes you will have to, but unless you need access to extra features on GitHub it won't cost you a thing.

Please post the full log as described in my signature.

Can you please post your full log as described in my signature?

It looks like the JSON file storing your island locations was corrupted