React & Express on Ubuntu

Hello guys
I am a web developer. I am developing simple web app using react & express on ubuntu.
I have a problem , code has been done.
it works well on win10, but does not work on ubuntu.
I am using "yarn dev" command....

this is package.json file in client directory

{
"name": "reactcrud",
"version": "0.1.0",
"private": true,
"dependencies": {
"@date-io/date-fns": "^1.3.13",
"@material-ui/core": "^4.11.0",
"@material-ui/icons": "^4.9.1",
"@material-ui/pickers": "^3.2.10",
"@testing-library/jest-dom": "^4.2.4",
"@testing-library/react": "^9.5.0",
"@testing-library/user-event": "^7.2.1",
"date-fns": "^2.16.1",
"react": "^16.13.1",
"react-dom": "^16.13.1",
"react-router-dom": "^5.2.0",
"react-scripts": "3.4.3"
},
"scripts": {
"start": "react-scripts start",
"build": "react-scripts build",
"test": "react-scripts test",
"eject": "react-scripts eject"
},
"eslintConfig": {
"extends": "react-app"
},
"browserslist": {
"production": [
">0.2%",
"not dead",
"not op_mini all"
],
"development": [
"last 1 chrome version",
"last 1 firefox version",
"last 1 safari version"
]
},
"proxy": "http://server.com:5000/",
"description": "This project was bootstrapped with Create React App.",
"main": "index.js",
"devDependencies": {},
"author": "",
"license": "ISC"
}

and this is package.json file for express

{
"name": "reactcurd",
"version": "1.0.0",
"scripts": {
"client": "cd client && npm run build && cd build && npm start",
"server": "nodemon server.js",
"dev": "concurrently --kill-others-on-fail \"yarn server\" \"yarn client\"",
"start": "node server.js"
},
"dependencies": {
"@material-ui/pickers": "^3.2.10",
"axios": "^0.20.0",
"body-parser": "^1.19.0",
"express": "^4.16.4",
"express-session": "^1.17.1",
"multer": "^1.4.2",
"mysql": "^2.18.1",
"nodemon": "^2.0.4",
"passport": "^0.4.1",
"passport-google-oauth": "^2.0.0",
"sync-mysql": "^3.0.1"
},
"main": "server.js",
"author": "",
"license": "ISC",
"description": ""
}

please help me...
Thank you...