When Alex’s Caves fails to launch, the fastest fix is usually not reinstalling everything. Work from the environment outward: Minecraft version, loader, dependency, mod file, then other mods.
Crash on startup
First check that the mod file targets the same Minecraft version and loader as the instance. A loader mismatch commonly produces immediate startup errors before a world opens.
Missing dependency message
Original builds can require Citadel. If the loader reports a missing dependency, install the compatible dependency rather than downloading unrelated “fix” files. Community ports may list a different requirement.
Duplicate mod warnings
Keeping an older and newer copy of the same mod in the mods folder can create duplicate-mod or version-selection errors. Move obsolete copies out of the instance and restart.
Works in single-player but not on server
Content mods usually need compatible files on the server and connecting clients. Compare the complete mod list, versions and loader family. A server-side startup log can reveal a different missing dependency than the client log.
New caves are not appearing
If you add a world-generation mod to an existing world, already explored chunks do not regenerate automatically. Test in new terrain or a fresh world before assuming the mod failed to load.
Next step
Return to the main compatibility section before downloading so you can compare edition, Minecraft version, loader and file type in one place.