Are you configuring the Railway service with the root of your domain?
-# e.g: example.com instead of www.example.com

yes

Then you need to proxy through cloudflare, hostinger doesn't natively support root level domain names

means?

You'll have to migrate your nameserver over to Cloudflare so that you can configure a root level domain

no

stepping in here to say that fragly is correct, you will need to use cloudflare's nameservers.

means I need to link my hostinger with cloudfare?

as fragly said, you need to use cloudflare's nameservers, cloudflare has a guide for that -

brother but I have already buy the hostinger

hostinger does not support root level cnames

already added hostinger for other 3 website it is working fine

this time getting this problem

you can use hostinger for subdomains but you cant use them for root domains

already used for root domain

I have an example also

with railway

its not something we officially support, and your domain will break at some point in the future because of it