Which ISPs and which DNS servers? You can also consider using a custom domain instead.

Currently your service is using the railway's beta "Metal Edge" network. dns resolution ends in "66.33.22.x"
Go to your service Settings -> Public Networking click the circle button when hovered says "Downgrade edge network".
Railway currently by default uses their "beta" Metal edge network which has some dns and routing issues which i have personally faced.

When you downgrade you switch back to GCP's network on which i am sure you will not face such problems.
Alternatively you could use cloudflare as a reverse proxy and point your custom domain to your railway service and achieve a similar result while still being on the Metal edge network.

Let me know if you need any further help.

I have downgraded the version but it seems there's still problem.

This cmd logs should explain better:
C:\Users\vipul>nslookup codeeditor-proxy-backend.up.railway.app

Server: UnKnown

Address: 192.168.15.217

*** UnKnown can't find codeeditor-proxy-backend.up.railway.app: Query refused

C:\Users\vipul>nslookup codeeditor-proxy-backend.up.railway.app 8.8.8.8

Server: dns.google

Address: 8.8.8.8

Non-authoritative answer:

Name: trestle.proxy.rlwy.net

Address: 35.213.168.149

Aliases: codeeditor-proxy-backend.up.railway.app

It honestly sounds like an issue with the ISPs DNS services rather than something caused by Railway (though I could be wrong!), which ISP is this? And are you able to try a custom domain at all?

You just changed it. give it some time. your system could be caching the previous dns query
try it again tomorrow.

It could be the problem of ISP's DNS (Though less chances of this).
I don't have any custom domain to test it for now.

Which ISP is it though?

custom domain wouldn't help here. ISP's ban domain for porn, torrents etc and not nobody's website.

It's the underlying dns that matters

You could try it but i doubt it will help.

I'm currently using JIO, But it's not that all JIO users are facing this issue. So, unable to understand what's the problem here.

Custom domain helps in a case where an ISP foolishly blocks *.up.railway.app domains when they see abuse on them and think that it will solve their problems with no repercussions (leading to many legit sites that suffer the consequences), and is something that happens routinely with every service that offers these kind of service subdomains for its users. A custom domain may not be blanket blocked in the same way. Enabling Cloudflare or similar proxy may also be required to hide the CNAME even further, depending how their blocks are implemented.

At first I thought that it will take some time to propagate to ISP's DNS but it's almost 24 hours now.

In this case all the JIO users should be affected with this though also possible that their device has custom DNS server set.

Leave it on GCP network and then try it again tomorrow morning

Hey guys!
It's still not working even on GCP network.
Any other solutions?
Check: https://codeeditor-proxy-backend.up.railway.app

Just put it behind cloudflare. They will handle everything. If nothing works cloudflare will.
I have all my services behind cf as it helps in routing, caching and provides an extra layer of ddos protection.
If you do not have a domain you can get a 6 digit .xyz domain for a dollar/year.

If you need help setting up cloudflare and pointing out a domain to your railway service then let me know.

Okay !
I think will have to do that there's no direct solution.
Accepting your solution for throughout help !