yarn start can't access /about page -> working fine on "yarn build"

Hello, I have a strange problem.

after clone react-static-boilerplate project from github and install all dependencies
and use $ yarn start, everything working fine except one thing,
When I click on "About" button it's not redirecting me to /about
it just change address and stay in home page,

When I use $ yarn build, and copy all files from public folder to my hosting it's working just perfect

but I want to test it in development mode (yarn start) on my vps
and there is weird stuff

fragment of my routes.json
```
{
"path": "/about",
"page": "./about"
},
```
but if I change my routes json to

```
{
"path": "/sign_up",
"page": "./sign_up",
"chunk": "main"
},
```
/about working in development mode (yarn start) but not working after yarn build and copy to static files to hosting

I don't understand that chunk option, any help please?

Start by reviewing routes.json and reproducing the navigation with yarn start, then compare it with the yarn build output. Trace how the /about route and the chunk option are handled in development versus generated static files; the issue is resolved when /about works in both modes.

Written by the indexing model from the issue text.