unable to register my on-premises Hyper-V server with Azure Site Recovery using the latest ASR Provider and a valid Vault Credentials file

Question

Category: Azure Site Recovery Issue Type: Hyper-V Registration Environment: On-premises Hyper-V (no VMM) Vault Name: (VaultName) Region: (RegionName)

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Issue Summary: Attempting to register an on-prem Hyper-V host with Azure Site Recovery fails consistently at the "Configuring Azure Site Recovery for registration" step. The installer reports:

"The ASR cannot be registered due to an internal error. Run Setup again to register the server."

The vault never receives the registration, and replication setup cannot proceed.

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Troubleshooting Steps Taken:

Created a Recovery Services Vault manually in (RegionName)

Downloaded a fresh Vault Credentials file and verified correct usage in the ASR wizard

Confirmed internet connectivity and DNS resolution from the Hyper-V host

Outbound access allowed to all required Microsoft FQDNs (e.g., *.blob.core.windows.net)

  DNS set to 8.8.8.8, flushed via PowerShell
  
  Disabled **Controlled Folder Access** and real-time protection during setup
  
  Installed the **latest ASR Provider and MARS Agent**
  
  Verified successful installation of both MSI packages
  
  Watched the registration fail with no clear UI error beyond “internal error”
  
  Log file (`DRASetupWizard_*.log`) reveals this:
  
  ```yaml
  nginx
  CopyEdit
  PUT https://pod01-id1.(region).backup.windowsazure.com/restapi/... → 400 Bad Request

InnerException: System.Net.WebException: The remote server returned an error: (400) Bad Request. ```

  Attempted full cleanup of prior installs and repeated with a new vault — same outcome
  

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Ask: Can someone from the Azure Site Recovery team help explain why registration might be failing with this generic internal error? The 400 suggests the request is malformed or invalid — but everything appears to match the documentation.

Is this a known backend issue, or is there a new process/requirement for registration that we may be missing?

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Blocking Use Case: We’re working on migrating our on-prem workloads via ASR and need to get this host registered to begin replication. Any help confirming the vault setup, credential validity, or backend registration service would be appreciated.

Answer 1

Hi Brendan Tween,

The registration failure with "400 Bad Request" typically occurs due to conflicts with prior configurations or incomplete cleanup of previous ASR registrations. follow below steps to resolve the Issue:

Manually delete the ASR registration key from the registry after uninstalling the provider. This resolves conflicts from residual configurations. link: https://learn.microsoft.com/en-us/troubleshoot/azure/site-recovery/getting-started/vault-registration-fails

Remove-Item -Path "HKLM:\SOFTWARE\Microsoft\Azure Site Recovery\Registration" -Recurse -Force

Download a new vault credentials file within 48 hours of registration attempts. Expired credentials often cause 400 errors.

Test connectivity to ASR endpoints beyond standard FQDNs:

Test-NetConnection pod01-id1.<region>.backup.windowsazure.com -Port 443

Replace <region> with your vault's actual region.

Create a new Recovery Services vault in the same Azure region as your Hyper-V hosts. This bypasses potential vault metadata corruption.

Reference:

https://learn.microsoft.com/en-us/azure/site-recovery/replication-appliance-support-matrix#network-requirements

https://learn.microsoft.com/en-us/azure/site-recovery/hyper-v-azure-tutorial

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