Error build react app and CORS error

Hello everyone,

I have the following problem : I try to put my web app on OVH. This web app work with Drupal and React. I have pu all my files on my OVH server. I can acces to my Drupal with my OVH url. But when I build my React app, I put him on my server, and I try to access from my url, I have a white screen without errors.

Here is a screenshot for my white screen :
!image|690x387

I have also some other error. When I try to launch my React app in my computer with my url localhost:300, I can get my app but when I try to do a call API, I have some CORS errors. How can I manage CORS for my site from OVH?

Here is a screenshot with my error :
!image|690x387

Thank for the help