SSL certificate not issued for subdomain despite correct DNS configuration - invalid

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1

Problem

SSL certificate is not being issued for my subdomain winkel.ehgn.nl, even though DNS is correctly configured. HTTP works, but shows a page without CSS.
HTTPS fails with SSL handshake error.

Setup

  • Domain: winkel.ehgn.nl (subdomain) and or shop.ehgn.nl
  • Root domain (ehgn.nl): Hosted elsewhere (not on Vercel)
  • Project: Astro SSR app, deploys successfully to ehgn-shop.vercel.app

DNS Configuration

Verification Done

  1. DNS resolves correctly:
    dig winkel.ehgn.nl CNAME +short
    → cname.vercel-dns.com.

  2. CAA records allow Let’s Encrypt:
    dig ehgn.nl CAA +short
    → 0 issue “letsencrypt.org”

  3. HTTP works (200 OK from Vercel):
    curl -I http://winkel.ehgn.nl
    → HTTP/1.1 200 OK
    → Server: Vercel

  4. HTTPS fails:
    curl -I https://winkel.ehgn.nl
    → SSL_ERROR_SYSCALL

What I’ve Tried

  • Removed and re-added domain in Vercel dashboard
  • Tried A record (76.76.21.21) instead of CNAME
  • Tried the CNAME value that Vercel gave me (new one, b5XXXXXXcname.)
  • Waited 24+ hours for certificate issuance
  • Ran vercel certs issue winkel.ehgn.nl → “Error: Response Error”
  • Ran vercel alias set → “Error: Response Error”

Vercel Dashboard Status

  • Domain shows “Invalid Configuration”
  • SSL Certificates section shows “No certificates to show”
  • DNS records section shows the domain pointing to correct IP

Environment

  • Vercel CLI: 50.4.8
  • Project type: Astro SSR with @astrojs/vercel adapter

Question

Why is the SSL certificate not being issued? The DNS is correct, CAA allows Let’s Encrypt, and HTTP traffic already reaches
Vercel. What’s blocking the certificate generation?

How can I fix it? For any subdomain white the root is hosted elsewhere.

2

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.

You can also use v0 to narrow down the possibilities.

3

In case it’s helpful, from our docs:

I recommend going through this guide as well:

I had a quick look, and it looks like your CSS file isn’t being called at all. Can you review that in your code? Feel free to ask v0.app for pointers directly connected to your codebase :slight_smile: