Technical specs
Craft to Exile [Dissonance] (2.15.1)
World Type TerraForged
RAM [10GB]

Describe Bug
When i try to start the server, it starts to Restart every few minutes with some errors, the server control panel says 3 mod errors found
More Overlays Updated has 2 errors
infinitemusic | - | 08th Mar 2022 22:04 PM | Found in crash report thread dump
More Overlays Updated | /mods/moreoverlays-1.17.5-mc1.15.2.jar | 08th Mar 2022 22:05 PM | Found in crash report thread dump
More Overlays Updated | - | 08th Mar 2022 22:05 PM | Caused by: net.minecraftforge.fml.ModLoadingException: More Overlays Updated has class loading errors
Crash Log: https://pastebin.com/kyPx438m
Edit 1:
Disabling More Overlays Updated lets the server start normally, unable to join the server with all mods enabled, one of the 2 mods disabled and both mods disabled, Error upon joining:
Internal Exception: io.netty.handler.codec.DecoderException: java.lang.IndexOutOfBoundsException: Index: 27, Size: 5

Follow these steps to set up a server. You can't use the client files to set up a server.
https://github.com/mahjerion/Craft-to-Exile-Dissonance/wiki/Server-Setup

Im using website called serverminer to host the modpack, so far it has installed correctly for: all the mods 6, Rlcraft, Mech & Magic
i will try to install it manually to see if it works

Tbh not sure how serverminer is doing it but they're using the client files for some reason. I can tell from the report. So they have some client only mods that don't belong and are causing the crashes. Hopefully your manual setup works!

I tried to manually upload the files but it keeps running into a error in
C:\Users\FireDragonSlayer\Desktop\serverprep\CrafttoExile-Dissonance-2.15.1-SERVER\config\ftbquests\quests\chapters
with the file ".snbt" it has no actual filename but has a extension of .snbt

i tried to make it a space, il edit this message if it works or not
Edit: Server started but unable to join, Same error as before, you sure that the server pack doesnt use the client side mods u mentioned?

Yeah, im quite sure the problem is in the server pack itself and not the server or the launcher im using, i had support from the server host manually install the server pack incase i messed up somewhere, server launched however unable to join the server due to Internal Exception: io.netty.handler.codec.DecoderException: java.lang.IndexOutOfBoundsException: Index: 27, Size: 5 error

Yes I'm very sure. I just triple checked. But this version has been out for a few months now and this is the first time it's cropping up. I dont really know why you're getting the error - try setting up the server on your own computer to test it (without using serverminer).

We've had issues in the past with serverminer and I think Aternos. Not sure why.

Also, the error you sent me with the quests tells me it's serverminer's uploading thing that's finnicky. Definitely try it on your own pc to confirm the cause. If it works on your PC it's probably serverminer, if it doesn't, it's possibly how you're setting it up. It is very very unlikely to be the server pack because it's worked for months and I use it on the official servers.

Turns out this whole problem is the combined fault of my mods being corrupted slightly which made me unable to join my own server but able to join the server you are running and singleplayer
original problem was also the problem of serverminer, what support said:
"Unfortunately, our CurseForge and Custom Modpack installers both use the client format for installation. This is because sadly there's no standard format for server installs yet, plus many modpacks don't even include separate server files.
The installer does do its best to disable any client-side mods that might cause issues, and while this usually works, sometimes a few mods slip past and cause errors."
The error i got after was most likely corrupted mods since after a reinstall i was able to join fine