heroku push rejected for a reactapp

I am trying to push a repository on Heroku but I receive the following error message :

remote: npm ERR! code EBADPLATFORM
remote: npm ERR! notsup Unsupported platform for fsevents@2.3.2: wanted {"os":"darwin","arch":"any"} (current: {"os":"linux","arch":"x64"})
remote: npm ERR! notsup Valid OS:    darwin
remote: npm ERR! notsup Valid Arch:  any
remote: npm ERR! notsup Actual OS:   linux
remote: npm ERR! notsup Actual Arch: x64
remote: 
remote: npm ERR! A complete log of this run can be found in:
remote: npm ERR!     /tmp/npmcache.FM9ZL/_logs/2021-03-22T20_17_38_119Z-debug.log
remote: npm ERR! code ELIFECYCLE
remote: npm ERR! errno 1
remote: npm ERR! backend@0.0.0 heroku-postbuild: `cd moodzle && npm install && npm run build`
remote: npm ERR! Exit status 1
remote: npm ERR! 
remote: npm ERR! Failed at the backend@0.0.0 heroku-postbuild script.
remote: npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
remote: 
remote: npm ERR! A complete log of this run can be found in:
remote: npm ERR!     /tmp/npmcache.FM9ZL/_logs/2021-03-22T20_17_38_183Z-debug.log
remote: 
remote: -----> Build failed
remote:        
remote:        We're sorry this build is failing! You can troubleshoot common issues here:
remote:        https://devcenter.heroku.com/articles/troubleshooting-node-deploys
remote:        
remote:        Some possible problems:
remote:        
remote:        - Node version not specified in package.json
remote:          https://devcenter.heroku.com/articles/nodejs-support#specifying-a-node-js-versio
remote:        
remote:        Love,
remote:        Heroku
remote:        
remote:  !     Push rejected, failed to compile Node.js app.
remote: 
remote:  !     Push failed
remote: Verifying deploy...
remote: 
remote: !       Push rejected to blooming-hamlet-25452.
remote: 

My front in React is named "moodzle" and is located in my backend project.

In my Back's package Json, I wrote :

"scripts": {
    "start": "node ./bin/www",
    "heroku-postbuild": "cd moodzle && npm install && npm run build"
  },

and in my app.js : app.use(express.static(path.join(__dirname, "moodzle/build")));

Can you please help me ?

Thank you !

Rache!