How to fix Error 1706 on Windows 11

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Troubleshooting Guide: Error 1706 – “The Endpoint Format Is Invalid”

Why This Error Happens

Error 1706 typically occurs when the Windows Installer service cannot locate a valid installation source path, often due to a malformed or corrupted RPC (Remote Procedure Call) endpoint string in the registry or installer cache. This can result from an incomplete software installation, a damaged Windows Installer package (.msi) reference, or corrupted entries in the HKEY_CLASSES_ROOT\Installer registry hive. In some cases, third-party installer tools or improperly formatted UNC paths during network-based installations can also trigger this error.

Step-by-Step Resolution Guide

Step 1: Verify and Repair the Windows Installer Service

  • Open Run (Win + R), type services.msc, and press Enter.
  • Locate Windows Installer, right-click, and select Restart.
  • Ensure the Startup type is set to Manual (not Disabled).
  • If the service fails to restart, run sfc /scannow in an elevated Command Prompt to repair corrupted system files.

Step 2: Clean and Reset the Installer Cache

  • Navigate to C:\Windows\Installer and back up the folder (do not delete files directly, as active installations may reference them).
  • Open Registry Editor (regedit) and go to HKEY_CLASSES_ROOT\Installer\Products.
  • Look for entries with malformed or unusually long GUID strings and note the associated product name.
  • Use the Microsoft Program Install and Uninstall Troubleshooter tool to safely remove the broken reference instead of manually deleting registry keys.

Step 3: Re-register the Windows Installer Engine

  • Open Command Prompt as Administrator.
  • Run the following commands in sequence:
  • msiexec /unregister
  • msiexec /regserver
  • Restart the computer to apply the re-registration.

Step 4: Check for Malformed UNC or Network Paths

  • If installing from a network share, confirm the path follows the correct format: \\ServerName\ShareName\Installer.msi.
  • Avoid mapped drive letters when running installers remotely, as Windows 11 sometimes fails to resolve them into valid RPC endpoints.
  • Copy the installer package locally to C:\Temp and run it from there instead.

Step 5: Update Windows and Installer Components

  • Go to Settings > Windows Update and install all pending updates, including optional driver and framework updates.
  • Ensure the Microsoft Visual C++ Redistributables and .NET Framework are up to date, as these often interact with the Installer service.

Alternative or Verification Steps

  • After completing the steps above, attempt to reinstall or repair the original application that triggered Error 1706. If successful, the installer should complete without RPC-related errors.
  • If the issue persists, boot into Safe Mode and attempt the installation again — this isolates the issue from third-party services or drivers that may be interfering with the Windows Installer’s endpoint resolution.