React-timestamp issue. Can't resolve 'react' in node modules - node.js

Question

I'm creating an App with React and everything has been fine for weeks until I installed react-timestamp with npm in order to convert unix time (https://www.npmjs.com/package/react-timestamp).
But now it won't compile and says:
/Users/nembokid/node_modules/react-timestamp/lib/timestamp.js
Module not found: Can't resolve 'react' in '/Users/nembokid/node_modules/react-timestamp/lib'
I've tried to remove package-lock.json as well as yarn.lock, then did npm install again followed by npm run start, but still same issue. Also tried to add it to my package.json file, but without success.
In '/Users/nembokid/node_modules/react-timestamp/lib' there's only one file: timestamp.js. Should it also contain a file called react.js?
How can I get around this? Should I try to delete react-timestamp from my node_modules folder? Don't really understand the issue here. Would be grateful for all help!
Edit: package.json:
{
"name": "client",
"version": "0.1.0",
"private": true,
"dependencies": {
"react": "^16.6.3",
"react-dom": "^16.6.3",
"react-router-dom": "4.3.1",
"react-scripts": "2.1.1",
"web3": "^1.0.0-beta.37"
},
"scripts": {
"start": "react-scripts start",
"build": "react-scripts build",
"test": "react-scripts test",
"eject": "react-scripts eject"
},
"eslintConfig": {
"extends": "react-app"
},
"browserslist": [
">0.2%",
"not dead",
"not ie <= 11",
"not op_mini all"
]
}

Answer 1

I deleted the folder /Users/nembokid/node_modules/react-timestamp and then from the terminal, inside the project client folder: npm run start without npm install or anything. Works perfectly fine again.