Error Failed to create Aml RP virtual workspace due to System.Exception: Failed async operation (404) when deploying Azure AI Foundry BYO private configuration

When deploying Azure AI Foundry using the Bring Your Own (BYO) private configuration, I encountered the following error:

│ RESPONSE 200: 200 OK
│ ERROR CODE: OperationError
│ --------------------------------------------------------------------------------
│ {
│ 'id': '/subscriptions/288a48ce-d888-4b1f-8bd9-a481811a27af/providers/Microsoft.CognitiveServices/locations/eastus2/operationResults/d72d3292-4c91-441a-9e6e-76b4a8a4bff9',
│ 'name': 'd72d3292-4c91-441a-9e6e-76b4a8a4bff9',
│ 'status': 'Failed',
│ 'startTime': '2025-10-17T12:23:48Z',
│ 'endTime': '2025-10-17T12:26:26Z',
│ 'error': {
│ 'code': 'OperationError',
│ 'message': 'Failed to Create the resource. Provisioning state: Failed',
│ 'details': [
│ {
│ 'code': 'ResourceProviderError',
│ 'message': 'Failed to create Aml RP virtual workspace due to System.Exception: Failed async operation {\n \'status\': \'Failed\',\n \'error\': {\n \'code\': \'InternalServerError\',\n \'message\': \'Received 404 from a service request\'\n }\n}\n at Microsoft.CognitiveServices.ResourceProvider.AmlRp.AsyncOperationHelper.PollUntilCompleteAsync[T](TraceContext traceContext, HttpResponseMessage response, HttpClient httpClient, Int32 timeoutInMin, CancellationToken cancellationToken) in /__w/1/s/src/Common/ResourceProvider/AmlRp/AsyncOperationHelper.cs:line 117\n at Microsoft.CognitiveServices.ResourceProvider.AmlRp.AmlRpClient.PutAmlRpVirtualHubAsync(TraceContext traceContext, Dictionary2 headers, ResourceIdentityInArm resourceIdentity, String primaryUserAssignedIdentity, String internalId, KeyVaultProperties keyVaultProperties, String subscriptionId, String resourceGroupName, String workspaceName, List1 networkInjections, PublicNetworkAccessType publicNetworkAccessType, CancellationToken cancellationToken) in /__w/1/s/src/Common/ResourceProvider/AmlRp/AmlRpClient.cs:line 119\n at Microsoft.CognitiveServices.ResourceProvider.AmlRp.AmlRpService.PutAmlRpWorkspaceAsync(TraceContext traceContext, ResourceRequestContext requestContext, WorkerMessageRequestContext workerMessageRequestContext, IResourceEntity insertedResourceEntity, CancellationToken cancellationToken) in /__w/1/s/src/Common/ResourceProvider/AmlRp/AmlRpService.cs:line 124\n at Microsoft.CognitiveServices.ResourceProvider.Worker.MessageProcessor.ProcessInternalAsync(TraceContext traceContext, RpWorkerQueueMessage message, CancellationToken cancellationToken) in /__w/1/s/src/ResourceProvider/Rp.WorkerRole/AccountProvisioning/MessageProcessor.cs:line 225'
│ }
│ ]
│ }
│ }

Before running the deployment, I ensured all the required resource providers were registered:

az provider register --namespace 'Microsoft.KeyVault'
az provider register --namespace 'Microsoft.CognitiveServices'
az provider register --namespace 'Microsoft.Storage'
az provider register --namespace 'Microsoft.MachineLearningServices'
az provider register --namespace 'Microsoft.Search'
az provider register --namespace 'Microsoft.Network'
az provider register --namespace 'Microsoft.App'
az provider register --namespace 'Microsoft.ContainerService'

I am using a Class A subnet (/24) delegated to Microsoft.App/environments.

Start by reproducing the Azure AI Foundry BYO private configuration deployment and review the reported OperationError response. Check the Azure CLI provider-registration commands and the AmlRp stack locations named in AsyncOperationHelper.cs, AmlRpClient.cs, and AmlRpService.cs. Done means identifying a reproducible cause and documenting or implementing a verified resolution.