Try to delete your node_module and reinstall all the package.

If your computer is MacOS, run brew install tailwindcss

I thought tailwindcss was moved into @tailwindcss/cli.

https://tailwindcss.com/docs/installation/tailwind-cli

npm install -D tailwindcss@3 postcss autoprefixer
npx tailwindcss init -p

It worked after running this command and add
@tailwind base;
@tailwind components;
@tailwind utilities;

in index.css

Perhaps VERSION 3 is what you need

my initial setup was just React 19 in Webpack, and i'm not going to install tailwind globally

1. install Tailwind CSS

npm install -D tailwindcss@3 postcss autoprefixer
npx tailwindcss init -p

3. Configure your template paths

make sure your content lists where your template files are. for me it is on src and it should detect the .js, or .jsx files

/** @type {import('tailwindcss').Config} */
module.exports = {
 content: ["./src/**/*.{js,jsx}"],
 theme: {
 extend: {},
 },
 plugins: [],
};

4. Add the Tailwind directives to your CSS

add these lines at the top of your index.css file

@tailwind base;
@tailwind components;
@tailwind utilities;

6. Import the css file

my index.css was already imported within index.js

4. start your build process

npm start

7. Start using Tailwind in your project

export default function App() {
 return (
 <h1 className="text-3xl font-bold underline">
 Hello world!
 </h1>
 )
}