Node.js Project Error Debugging

I need an experienced Node/Express developer to address a small issue with my Node.js project. The project fails immediately when running npm start with a "Module not found" error.

Requirements:
- Reproduce the error locally
- Identify root cause(s)
- Provide a short fix and brief explanation

Ideal Skills:
- Strong expertise in Node.js and Express
- Experience with npm and package management
- Proficient in debugging Node.js applications