Hello! Our production domain sigmaclub.ru is inaccessible from our affected connection in Russia. Please help distinguish an edge/custom-hostname issue from upstream filtering. Tests were performed September 8–9, 2026.
Configuration: Hobby project sigma-pro; active Reg.ru registration; Cloudflare DNS only (not proxied), apex and www A 76.76.21.21. Vercel certificates expire November 6, 2026. External SSL Labs scan of 76.76.21.21 completed with A+. No custom firewall rules, IP blocks or Attack Mode were found enabled.
Symptoms: Chromium ERR_CONNECTION_CLOSED; Windows curl/Schannel and Node report termination before TLS completes, not HTTP 403. Through the same working HTTP proxy with destination fixed to 216.198.79.1, TLS with SNI sigma-pro.vercel.app succeeds and returns HTTP 308; SNI sigmaclub.ru disconnects. The alias redirects to the custom domain, so is not a browsing workaround. Other websites work through this proxy. The owner also tested without VPN and the site still failed. This does not prove worldwide failure or identify the responsible network.
Some alternate Vercel IP tests returned HTTP 200 but stopped at 16,604 of 28,101 bytes and timed out; a small /v7-release.json completed.
We tried the project-recommended CNAME 53778313c6d60140.vercel-dns-017.com for apex and www, verified propagation and Valid Configuration in Vercel, but access did not improve. We restored both A records to 76.76.21.21, DNS only. No reverse proxy was enabled and TLS/security settings were not weakened.
Could someone verify hostname/certificate mapping and any edge-level restriction, or suggest a diagnostic that conclusively separates this from upstream filtering? We are not claiming Vercel is blocking the site. We want a supported remedy while staying on Vercel, not arbitrary IP changes. Thank you.
