Unable to install SQL Express 2005 onto Windows 10 via hyper-v packer

I have successfully copied the SQL Express installer (exe) onto my hyper-v VM as its being set up by packer, but the actual installation batch file seems to not succeed. Below is my packer configuration file:

      "scripts": [
      "type": "powershell"
      "script": "./scripts/storeservices/InstallQuest-SQL2K16x64.bat",
      "pause_before": "15m"

The copy script works, then the installation script ‘appears’ to complete (e.g. when I look at the packer log, I can see the echo before and after the install line from the batch file)

@Echo off
ECHO [StoreServices] Beginning SQL Express installation...
ECHO [StoreServices] Finished SQL Express installation...

packer log:

    hyperv-iso: Installing AWS Tools...
    hyperv-iso: Creating AWS credentials...
    hyperv-iso: Copying SQL setup file(s) to local machine...
    hyperv-iso: LastWriteTime : 7/17/2021 9:48:22 PM
    hyperv-iso: Length        : 459167776
    hyperv-iso: Name          : SQLEXPR_x64_ENU.exe
==> hyperv-iso: Pausing 15m0s before the next provisioner...
==> hyperv-iso: Provisioning with windows-shell...
==> hyperv-iso: Provisioning with shell script: ./scripts/storeservices/InstallQuest-SQL2K16x64.bat
    hyperv-iso: [StoreServices] Beginning SQL Express installation...
    hyperv-iso: [StoreServices] Finished SQL Express installation...
==> hyperv-iso: Gracefully halting virtual machine...

However when I use vagrant to stand up the produced .box file and attach it as a hyper-v VM, SQL express is not installed. The ‘exe’ file is in the temp folder as expected, and I can see all other scripts execute OK, but SQL express is not installed. If I run the batch file on the VM manually, SQL Express installs OK.

What am I missing here? :frowning:

Is there anyone who could suggest something? This is I think my 3rd topic in this forum, and it seems I am yet to have a single response from anyone about anything. Is there perhaps a better place to target my question? I tried Stack Overflow but they complained about me asking packer questions there.