@Ian V Thanks for the update.
Based on my experience, if the win32 app is installed successfully, it means that the deployment method is correct. From the information that you provided, the win32 app is installed successfully during the Autopilot phase, but it has someting wrong when launching the app.
Given this situation, it is needed to check more background information such as log analysis to find the root cause. With Q&A limitation, Q&A is not the best channel for such log analysis case. So, we suggest to open an online support ticket to handle this issue more effectively. It is free. Here is the online support link and hope it helpful.
https://learn.microsoft.com/en-us/mem/intune/fundamentals/get-support
Also, here is a reference link about win32 app troubleshooting:
https://learn.microsoft.com/en-us/troubleshoot/mem/intune/troubleshoot-app-install#win32-app-installation-troubleshooting
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