A mod wants a different Minecraft version
Applies to Fabric, Quilt.
What it looks like in your log
Mod 'Lithium' (lithium) 0.12.1 requires version 1.20.1 of 'Minecraft' (minecraft), but only the wrong version is present: 1.20.4!
What causes it
A mod requires a Minecraft version other than the one this server runs.
How to fix it
Swap the mod for the build made for your Minecraft version, or change the server version to match the mod.
Not sure this is your problem? Paste your log and Roastd will tell you which of these it actually matched, and what else it found.
Check your own log