AWS API Gateway: 403 MissingAuthenticationTokenException for /static/js/bundle.js even though Authorization is set as None

I have set up this flow:

external world --> AWS API Gateway ---> VPC Link ---> Network Load Balancer ---> my single EC2 instance

The API Gateway is working because when I input the custom domain in my browser, it successfully visits the frontend service running on my EC2 instance.

However, for /static/js/bundle.js, I'm getting a 403 MissingAuthenticationTokenException error:

But the request to the main domain is ok:

Also, all other resources failed: /static/js/vendors~main.chunk.js

static/js/main.chunk.js

/favicon.ico

/manifest.json

My frontend is written in React JS.

Note that it says: x-amzn-errortype: MissingAuthenticationTokenException. But I have set the Authorization to be None:

What is going on?