Problems with a new AKS Cluster and AzureDefaultCredentials()

[ThomasErvik]

Created a new AKS Cluster in region and we get the following error when deploying our pods:

`"Unhandled exception. Azure.Identity.CredentialUnavailableException: DefaultAzureCredential failed to retrieve a token from the included credentials. See the troubleshooting guide for more information. https://aka.ms/azsdk/net/identity/defaultazurecredential/troubleshoot

• EnvironmentCredential authentication unavailable. Environment variables are not fully configured. See the troubleshooting guide for more information. https://aka.ms/azsdk/net/identity/environmentcredential/troubleshoot
• WorkloadIdentityCredential authentication unavailable. The workload options are not fully configured. See the troubleshooting guide for more information. https://aka.ms/azsdk/net/identity/workloadidentitycredential/troubleshoot
• ManagedIdentityCredential authentication unavailable. The requested identity has not been assigned to this resource.
• Visual Studio Token provider can't be accessed at /app/.IdentityService/AzureServiceAuth/tokenprovider.json
• Azure CLI not installed
• PowerShell is not installed.
• Azure Developer CLI could not be found.
  ---> System.AggregateException: Multiple exceptions were encountered while attempting to authenticate. (EnvironmentCredential authentication unavailable. Environment variables are not fully configured. See the troubleshooting guide for more information. https://aka.ms/azsdk/net/identity/environmentcredential/troubleshoot) (WorkloadIdentityCredential authentication unavailable. The workload options are not fully configured. See the troubleshooting guide for more information. https://aka.ms/azsdk/net/identity/workloadidentitycredential/troubleshoot) (ManagedIdentityCredential authentication unavailable. The requested identity has not been assigned to this resource.) (Visual Studio Token provider can't be accessed at /app/.IdentityService/AzureServiceAuth/tokenprovider.json) (Azure CLI not installed) (PowerShell is not installed.) (Azure Developer CLI could not be found.)
  ---> Azure.Identity.CredentialUnavailableException: EnvironmentCredential authentication unavailable. Environment variables are not fully configured. See the troubleshooting guide for more information. https://aka.ms/azsdk/net/identity/environmentcredential/troubleshoot
  at Azure.Identity.CredentialDiagnosticScope.FailWrapAndThrow(Exception ex, String additionalMessage, Boolean isCredentialUnavailable)
  at Azure.Identity.EnvironmentCredential.GetTokenImplAsync(Boolean async, TokenRequestContext requestContext, CancellationToken cancellationToken)
  at Azure.Core.Pipeline.TaskExtensions.EnsureCompleted[T](ValueTask1 task) at Azure.Identity.EnvironmentCredential.GetToken(TokenRequestContext requestContext, CancellationToken cancellationToken) at Azure.Identity.DefaultAzureCredential.GetTokenFromSourcesAsync(TokenCredential[] sources, TokenRequestContext requestContext, Boolean async, CancellationToken cancellationToken) --- End of inner exception stack trace --- ---> (Inner Exception #1) Azure.Identity.CredentialUnavailableException: WorkloadIdentityCredential authentication unavailable. The workload options are not fully configured. See the troubleshooting guide for more information. https://aka.ms/azsdk/net/identity/workloadidentitycredential/troubleshoot at Azure.Identity.WorkloadIdentityCredential.GetTokenCoreAsync(Boolean async, TokenRequestContext requestContext, CancellationToken cancellationToken) at Azure.Identity.CredentialDiagnosticScope.FailWrapAndThrow(Exception ex, String additionalMessage, Boolean isCredentialUnavailable) at Azure.Identity.WorkloadIdentityCredential.GetTokenCoreAsync(Boolean async, TokenRequestContext requestContext, CancellationToken cancellationToken) at Azure.Core.Pipeline.TaskExtensions.EnsureCompleted[T](ValueTask1 task)
  at Azure.Identity.WorkloadIdentityCredential.GetToken(TokenRequestContext requestContext, CancellationToken cancellationToken)
  at Azure.Identity.DefaultAzureCredential.GetTokenFromSourcesAsync(TokenCredential[] sources, TokenRequestContext requestContext, Boolean async, CancellationToken cancellationToken)<---

---> (Inner Exception #2) Azure.Identity.CredentialUnavailableException: ManagedIdentityCredential authentication unavailable. The requested identity has not been assigned to this resource.
---> MSAL.NetCore.4.66.1.0.MsalServiceException:
ErrorCode: managed_identity_request_failed
Microsoft.Identity.Client.MsalServiceException: [Managed Identity] Authentication unavailable. Either the requested identity has not been assigned to this resource, or other errors could be present. Ensure the identity is correctly assigned and check the inner exception for more details. For more information, visit https://aka.ms/msal-managed-identity.
Status: BadRequest
Content:
{"error":"invalid_request","error_description":"Multiple user assigned identities exist, please specify the clientId / resourceId of the identity in the token request"}"`

We have multiple other AKS Clusters with the same setups and we do not get this problem there.
What have we done wrong?

az aks show --name aks-name --resource-group rg --query 'identity' returns 1 identity:
{ "delegatedResources": null, "principalId": "guid", "tenantId": "guid", "type": "SystemAssigned", "userAssignedIdentities": null }