Partial script not running while deployment

Seems environment variable not persisting because the Custom Script Extension runs in a transient process context. When you use Set-Item Env:\Path, it only updates the environment for that running PowerShell session. Once the extension finish, the VM boots into a fresh session and the change is gone. To make PATH (or any env var) stick across reboots and be visible to all processes, you may require to write it to the machine-level environment registry or use [System.Environment]::SetEnvironmentVariable() with the right scope.