Custom domain stuck in "Validating domain ownership" state

Question

AI bot send me here:

Domain: agenda-positiva.com
    Previously hosted on Vercel with HSTS enabled
    Validation stuck in Railway
    Browsers getting HSTS security errors
    DNS is correctly configured

This is beyond normal troubleshooting — Railway's support team needs to manually intervene to:

Force domain validation to complete
    Issue an SSL certificate
    Clear any cached validation issues