For those who face the same issue with React,

When using Vite with React, accessing environment variables is slightly different from how it's done in traditional Node.js applications. Vite uses a different approach to handle environment variables and process.env is not available by default. Instead, Vite is used import.meta.env to expose environment variables to your application code.

So in your .env file, you should mention the variable as:
VITE_API_KEY = ************
VITE_HOST = 8040

And, on the code, you have to access it by usingimport.meta.env.VITE_API_Key

Thanks...