The provided download is a source branch archive
The download URL supplied for this site points to a GitHub branch archive ending in .zip. A source archive is useful for code inspection and development, but it is not automatically the same as a compiled mod JAR intended for a normal mods folder.
Four checks before any installation
Confirm the Minecraft version, the mod loader, required dependencies and whether the file is a compiled release. Back up worlds and configuration files before changing a stable setup.
How to test without risking your main world
Use a separate instance or copied profile. Start with a fresh test world, confirm the expected survival systems load, and only then consider opening an important save.