Custom domain inaccessible from one US ISP/location, while .vercel.app URL works

(edited)

My Vercel deployment URL works correctly, but my custom domain does not work for a friend in MI, US. The domain works perfectly from my location in Asia, and I am not sure whether other locations are affected as well.

Custom domain: www.nexorasystems.xyz

The Vercel deployment URL works from the affected network: aamina-enterprises-eacnni0gf-bahadurkhan10s-projects.vercel.app

DNS configuration:

A record: @ → 76.76.21.21

CNAME: www → 169ad3c74fdc89f9.vercel-dns-017.com

The root domain resolves to 76.76.21.21

The www domain resolves to these Vercel IPs: 216.198.79.1 216.198.79.65 64.29.17.1 64.29.17.65

The issue is:

The .vercel.app deployment URL works for him
The custom domain does not work
The issue appears to be specific to a particular network/location
The affected user is located in Michigan, USA

I have seen similar reports of Vercel custom domains being inaccessible from specific networks or locations while the .vercel.app deployment URL works normally.

The possible solutions I have found so far are:

Changing the DNS resolver, which may not be a practical solution if multiple users are affected
Contacting Vercel support or posting on the Vercel Community

Has anyone experienced and solved this type of issue before? I would really appreciate any help or insight into what could be causing it.

The domain troubleshooting guide can help with most custom domain configuration issues. You might be able to use that guide to solve it before a human is available to help you. Then you can come back here and share the answer for bonus points.

https://vercel.com/docs/domains/troubleshooting

vercel.com

Troubleshooting domains

Learn about common reasons for domain misconfigurations and how to troubleshoot your domain on Vercel.

Leaderboard Winner

Hi Bahadurkhan10,

Since the .vercel.app URL works from the affected network, I’d separate the app/deployment from the custom-domain network path.

For www.nexorasystems.xyz, the apex A record is not the main thing being used. The important record is the www CNAME, and it should match the exact value shown in Vercel’s domain settings.

I’d ask your friend in Michigan to run these from the affected network:

dig CNAME www.nexorasystems.xyz +short
dig A www.nexorasystems.xyz +short
curl -4Iv --connect-timeout 10 https://www.nexorasystems.xyz/
curl -4Iv --connect-timeout 10 https://aamina-enterprises-eacnni0gf-bahadurkhan10s-projects.vercel.app/

If the .vercel.app URL connects but the custom domain times out, that points away from your app code and more toward DNS resolution, ISP routing, or the specific Vercel edge path used by the custom domain.

If curl gets any Vercel response, the useful header to capture is:

x-vercel-id

If it only times out, I’d also test the resolved custom-domain IP over TCP 443:

mtr -4 -T -P 443 -c 20 www.nexorasystems.xyz

The most useful follow-up would be the affected user’s dig, curl -Iv, and mtr output, plus whether the same domain works for them on mobile data or a different DNS resolver.

Adding another data point since this looks like the same class of bug: same symptom for us (apexcore.academy, project apex-dashboard, team apexcore1) — vercel.app works, custom domain resets during TLS handshake. In our case it is 100 percent reproducible as region-specific: every US connection fails, every Mexico connection succeeds, including a real student who used the site normally from there. We also reproduced the identical failure on a second, brand new domain pointed at the same project, so it is not a per-domain DNS misconfiguration, it looks like something at the project/edge level. Sev1 support case #01dfSHskjdcVaEhj has been open 20+ hours with no reply. This is a production app with paying users down on its main domain, so any visibility from an engineer would help a lot.