npm start not working in create-react-app: missing script:start - reactjs

Question

I tried to update my version of create-react-app by doing this:
If you've previously installed create-react-app globally via npm
install -g create-react-app, we recommend you uninstall the package
using npm uninstall -g create-react-app to ensure that npx always uses
the latest version.
But now, when I run npm start, i get an error message:
missing script: start
But in the package.json from my app, i found the start script:
{
"name": "dropzone-montessori",
"version": "0.1.0",
"private": true,
"dependencies": {
"react": "^16.12.0",
"react-dom": "^16.12.0",
"react-scripts": "3.2.0"
},
"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"
]
}
}
Anybody knows what's happening?