Databricks: Unable to Attach Notebook to Serverless GPU Compute — AI Runtime Not Available Error

Problem description

Attaching a notebook to serverless GPU compute (AI Runtime) in our Azure Databricks workspace fails for all users. The UI displays a generic attachment error, while the underlying HTTP 400 response states:

BAD_REQUEST: AI Runtime is not available. To access this feature, please contact sales for assistance.

Environment

• Azure Databricks workspace in East US.
• Notebook-based workflow requiring serverless GPU compute.
• Provisioned directly through Azure, with no existing Databricks sales relationship.
• Standard serverless CPU compute works successfully.

What I've already tried

• Created a new notebook using standard serverless CPU compute and confirmed successful execution.
• Confirmed that serverless GPU attachment fails across users.
• Inspected browser network requests and identified the underlying HTTP 400 error.
• Enabled advanced diagnostics for Microsoft Support.
• Provided subscription information, workspace URL, notebook ID, and configuration screenshots through the support case.

Microsoft Support suggested a workspace-level availability or enablement restriction but has not confirmed the specific cause or provided enablement steps. The support workflow has now directed me to Microsoft Learn Q&A.

Current status

Serverless GPU access remains blocked. I need confirmation of:

1. Whether serverless GPU / AI Runtime is supported for our workspace's region and configuration.
2. The specific restriction causing the request to be rejected.
3. The steps required to enable access and the team responsible for doing so.
4. How an Azure customer without an existing Databricks sales contact can obtain the required enablement.

Standard serverless CPU has already been validated. Using CPU or a regular GPU cluster does not resolve the request for serverless GPU access.