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

Update: I found additional evidence that may help identify the cause.

The official Roskomnadzor restriction-checking service returns:

No results for my domain: xn----htbdko2afjj.xn--p1ai (тур-лидер.рф). A restriction record when searching for 216.198.79.1, the IP used by my apex A record. The displayed date is March 4, 2024.

Both screenshots are attached. This suggests a possible shared-IP restriction, although it does not establish the exact cause of the connection failures.

The issue now also affects home Wi-Fi, and using a VPN has not resolved it in my recent tests. The browser reports: net::ERR_CONNECTION_CLOSED 200 (OK)

The same deployment works through tour-leader.online and tourleader.vercel.app. Both the apex and www versions of the .рф domain fail for me. Connecting www directly to Production instead of redirecting it to the apex did not help.

I have now changed the apex A record from 216.198.79.1 to 76.76.21.21 as a temporary workaround. I am waiting for DNS propagation and have not yet confirmed whether this resolves the issue.

Could the Vercel team please confirm:

Is 76.76.21.21 still a supported address for this project? Is there another supported DNS target or routing option if this address is also unreachable? Can you investigate the connection failures affecting these custom domains?

Project: tourleader Deployment domain: tourleader.vercel.app

Thank you.