DaemonUmbra

Please provide a full debug.log as described in the EAQ and the logs section of my signature below

1.12 is no longer supported on this forum. Please update to a modern version of Minecraft to receive support.

Please don't hijack other people's threads.

1.12 is no longer supported on this forum. Please update to a modern version of Minecraft to receive support.

1.12 is no longer supported on this forum. Please update to a modern version of Minecraft to receive support.

1.12 is no longer supported on this forum. Please update to a modern version of Minecraft to receive support.

Please don't necro old threads

Even if you have Java 8 installed, you apparently also have Java 13 installed and that is what your computer is using to run jar files

Twitch is not very reliable when it comes to setting Forge up correctly I'm afraid. I'd recommend using the method detailed in the video in the logs section of my signature below, it's how to run a Twitch pack without using Twitch

1.12 is no longer supported on this forum. Please update to a modern version of Minecraft to receive support.

Please provide the installer log using one of the paste sites listed in the logs section of my signature below

Please stop editing your server log before sending it

Really old Minecraft versions are no longer supported on this forum. Please update to a modern version of Minecraft to receive support.

Twitch seems ok at distributing their mods and not much else. Personally I use Twitch only to install packs, then I set the GameDir to the modpack dir and use the regular launcher

Please stop bumping your thread. Just make sure the server and your client are stopped, start both, reproduce the issue, stop both, then provide the debug.log from both.

The Logs section of my signature has a video on running Twitch packs without Twitch, I would recommend trying that

1.12 is no longer supported on this forum. Please update to a modern version of Minecraft to receive support.

Changing the GameDir doesn't tell the launcher to use Forge, it tells it where to look for saves, logs, configs, screenshots, mods, etc. You tell it to use Forge by changing the Minecraft Version to a Forge version

1.12 is no longer supported on this forum. Please update to a modern version of Minecraft to receive support.

1.12 is no longer supported on this forum. Please update to a modern version of Minecraft to receive support.

Can you provide a screenshot?

Please provide debug.log as described in the EAQ and the Logs section of my signature below

1.12 is no longer supported on this forum. Please update to a modern version of Minecraft to receive support.

It's running with Java 13... I think the -v argument for invoking Java was removed a couple versions back

1.12 is no longer supported on this forum. Please update to a modern version of Minecraft to receive support.