Azure App Service default hostname returns authoritative DNS NXDOMAIN despite app being healthy

Hello Microsoft Azure community,

We are experiencing a DNS resolution issue with an Azure App Service (Linux, Node.js 24) deployed in the Switzerland North region.

Problem

The Azure-assigned default hostname returns NXDOMAIN, even though the App Service is running and Azure reports it as healthy.

Environment

• Service: Azure App Service (Linux)

Region: Switzerland North

Runtime: Node.js 24 LTS

App Service plan: Basic B1

Authentication: Microsoft Entra ID enabled

Default hostname: Azure-generated, region-specific *.switzerlandnorth-01.azurewebsites.net

Observations

Azure Portal reports the App Service as Running, with a healthy runtime and Health Check showing 100% healthy.

The default hostname is listed in the App Service configuration and shown as verified.

GitHub Actions successfully builds and deploys the application using Azure OIDC authentication.

The final deployment verification fails with curl: (6) Could not resolve host.

DNS lookups using public resolvers, including 1.1.1.1, return NXDOMAIN.

Direct DNS queries to Azure's authoritative name servers (ns1-34.azure-dns.com, ns2-34.azure-dns.net, ns3-34.azure-dns.org, and ns4-34.azure-dns.info) also return authoritative NXDOMAIN.

A test using curl --resolve to connect directly to the App Service's reported inbound IP address reached the HTTP endpoint but returned 404 Site Not Found.

Question

Could this indicate an issue with Azure-managed DNS registration or hostname provisioning for the App Service?

What is the recommended way to investigate or restore DNS resolution for an Azure-assigned default hostname without recreating the App Service or disrupting its existing configuration?

We would appreciate guidance on any additional diagnostic steps that can be performed from the Azure Portal or Azure CLI.

Thank you.