A mod needs another mod that is not installed

[09:12:41] [main/ERROR] [ne.mi.fm.lo.ModSorter/LOADING]: Missing or unsupported mandatory dependencies:
	Mod ID: 'balm', Requested by: 'waystones', Expected range: '[7.3.0,)', Actual version: '[MISSING]'
	Mod ID: 'geckolib', Requested by: 'mowziesmobs', Expected range: '[4.4.2,)', Actual version: '[MISSING]'

What it means

Every mod declares what it needs to run: other mods (a library such as Architectury, Cloth Config or GeckoLib), a range of Minecraft versions and a range of loader versions. Before any mod starts, the loader checks that list. When something is missing, or present in a version the mod does not accept, the loader refuses to go on and the server stops before the world loads.

The loader usually lists every problem at once. The diagnosis reports them as one issue per run, names the first dependency that is not installed, and lists the rest. A dependency that is installed in the wrong version is named only when nothing is missing outright: the loader often adds Minecraft in a refused version next to the libraries a mod lacks.

Why it happens

• A library was not added. Many mods ship their shared code as a separate mod, and the modpack or the mods folder has the mod but not its library.
• A mod was removed that another mod still needs.
• Versions do not fit. The dependency is installed, but older or newer than the range the mod asks for, often after updating one mod and not the other.
• The mod is made for another game version. It needs a Minecraft or loader version the server does not run, so the dependency named is minecraft, forge, neoforge or fabricloader.

How to fix

1. Read the issue’s missing and mod: the first is what to add, the second is what needs it. The full list is in dependencies and in the log.
2. Add each missing mod in a version made for the server’s Minecraft version and loader. The mod’s page (Modrinth or CurseForge) lists its required dependencies.
3. If a dependency is installed but in the wrong version, update or downgrade it to fit the range the log prints (Expected range on Forge and NeoForge, requires version ... on Fabric and Quilt).
4. If the dependency is minecraft or the loader itself, use the version of the mod made for your Minecraft version, or remove that mod.
5. Forge and NeoForge: the ranges use Maven notation: [9.1,) means 9.1 or newer, [1.20,1.21) means 1.20 up to, but not including, 1.21.
6. Fabric and Quilt: the loader prints “A potential solution has been determined” above the details, with the installs or replacements it suggests.

In Perland

The issue appears in the server’s Diagnosis tab with the mod and the dependency it lacks. On a server whose mods come from a modpack, the fix button leads to the server’s Sources, and Mod Studio is where you add, update or remove the pack’s mods; it adds a mod’s required dependencies for you. Otherwise, add the missing jar to the mods folder in the Files tab.

References

• Forge documentation: mod files and dependencies
• NeoForge documentation: mod files
• Fabric wiki: fabric.mod.json (depends)