DaemonUmbra

1.8.9 is no longer supported on this forum due to its age. Please update to a modern version of Minecraft to receive support. Also: You CAN have more than one Forge

Forge installs itself as a version of Minecraft. Make a new Profile/Installation and select Forge from the version dropdown. (Note: For some reason Forge 1.12.2 gets booted to the bottom of the list.)

BetterAnimalsPlus was designed for a beta version of Forge and may need to be updated to work with the version you have, check for such a version

Try repairing the profile, Twitch has a habit of screwing up Forge's installation procedure

Try 28.1.10

You launched vanilla Can you supply a screenshot of the profile's details?

Please use one of the sites listed in my signature, the site you used immediately asks me to agree to sharing my data which creeps me out

Try the previous version of Forge

This looks as simple as making sure your client and server have the same version of the pack

Threads merged. Your ToughAsNails config is apparently invalid.

You know you need to run the Forge jar and not the Vanilla jar to start a Forge server, right?

You started a Vanilla server, not a Forge server

Please read the Logs section of my signature below and provide the appropriate log in the appropriate manner.

What do you mean by a "Mod button"?

Try repairing the modpack instance, Twitch has a habit of screwing up Forge's installation process

That actually brings this to a close because 1.7.10 isn't actively supported anymore. Please update to a modern version to receive support.

If you had scrolled up you would have seen this:

It's not that it's broken in any serious way, but some things require their environment to be just so, and Advent of Ascension requires 1.12.2

That's on your computer, not the server

It's scanning the mods directory, but not the mod files

Can I ask why you're running 1.12 specifically and not 1.12.2?

The first error can be fixed by running the game with Java 8

It's not even scanning the files for mods, it's safe to assume you've tried restarting the game, right?

debug.log, it's a Forge log but no vanilla log will have enough info

Please provide debug.log as described in my signature