CORS error: Response to preflight request - No 'Access-Control-Allow-Origin' header is present on the requested resource


I’m getting this error when I try to make a GET request from our React application to our discourse installation.

Access to XMLHttpRequest at '' from origin 'http://localhost:3000' has been blocked by CORS policy: 

Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource.

I have already enabled CORs for localhost:3000, so I’m not sure what else I can do. Any help would be greatly appreciated!


PS: For context, I am not self-hosting discourse.