Custom domain fails on Jio India; vercel.app host works

Project: holistichealthcare (Hobby plan). Observed 24 September 2026.

A user in India can open https://holistichealthcare.vercel.app/ on a Jio-connected phone and laptop, but https://www.hhcare.eu.com/ fails. Phone Chrome showed DNS_PROBE_FINISHED_NXDOMAIN; laptop Chrome showed ERR_TIMED_OUT. The apex https://hhcare.eu.com/ redirects (308) to https://www.hhcare.eu.com/. Airtel difficulty has also been reported, but that path is less well documented.

Holistic Health Care

Holistic Health Care | Better Health, Better Life

Find doctors, book appointments, access therapy and medicine support, and explore health courses through one trusted health care platform.

New isolation test: the same doctor’s phone reportedly opens the production site and doctor profile on the site owner’s hotspot, then fails again on the doctor’s own mobile Internet. This points to a network-dependent path, but does not by itself distinguish DNS, routing, or filtering.

Vercel’s dashboard lists the apex, custom domain and alternate deployment hostname as Valid Configuration. Google and Cloudflare public DNS resolve CNAME www.hhcare.eu.com -> dbe0367bf6912afe.vercel-dns-017.com and Vercel A records. From our location HTTPS returns 200. Several sampled Jio/Airtel probes in India also returned 200. One Thane Jio probe briefly timed out through its system resolver, returned 200 using Google DNS, and later recovered. This is not a reproduction of the doctor’s exact failure.

Globalping measurement IDs: www DNS 2OQv6TpFX55vbtyL300021C63; www HTTPS 2Qv72bIkrLqgHHC6H00021C64; alternate HTTPS 2jnCImMDiSjGcW1L300021C64; Thane with Google DNS 2lB64OoojL4aLMt0l00021C64.

Has anyone seen this combination where a Vercel hostname works but a custom domain fails on a particular Indian mobile network? Which supported diagnostics or remediation would you recommend while the production configuration is marked valid? We do not have the affected user’s exact resolver, public IP, city, or traceroute.