Since the DCA (Desktop Companion Application) MSI is failing even during a manual install, we can rule out SCCM/ConfigMgr as the culprit. This is a local execution failure. Error 1603 is a "catch-all" for a fatal error, and 0x80073CF9 is commonly associated with AppX or sandboxed installation failures and can surface when an MSI invokes a failing custom action or registration step or a permissions issue with the installation directory.
Here is the recommended troubleshooting path:
1. Perform a "Clean Slate" Uninstall
MSI failures are often caused by "zombie" registry keys from previous versions.
Manual Cleanup: Check Program Files, ProgramData, and user AppData for leftover DCA folders and delete them.
Registry: Check HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall for any orphaned DCA ProductCodes.
Tooling: If standard cleanup is insufficient, use the Microsoft Program Install and Uninstall Troubleshooter to scrub the old version out of the registry.
2. Verify Permissions and Context
Admin Rights: Run the Command Prompt as Administrator before launching the MSI.
Exclusions: Temporarily disable any aggressive EDR/Antivirus (like CrowdStrike or Defender for Endpoint) that might be blocking the installer's "Custom Actions" from executing.
3. Confirm Version & Dependencies
Verify that this specific DCA version is compatible with your current Windows build and Dynamics 365 release.
Check for required .NET Framework versions or C++ Redistributables that might be missing on the target machine.
4. Generate and Analyze a Verbose Log
To find the exact root cause, run the installer via command line with logging enabled:
msiexec /i "DCA_installer.msi" /L*v "C:\temp\dca_debug.log"
How to read the log:
Open the file and search for "Return Value 3". The lines immediately above the first instance of "Return Value 3" will tell you exactly which Custom Action failed. This is the "smoking gun" you’ll need for a support ticket.
5. Escalation
If the failure persists on a clean, "vanilla" machine that isn't joined to your domain, it’s highly likely a vendor defect in the MSI packaging. At that point, collect your verbose logs and raise a ticket with Microsoft Support, as it's likely an issue with the installer's logic rather than your environment. Since the issue reproduces consistently across multiple machines and install contexts, environmental variance is unlikely.
What does Microsoft documentation say?
Microsoft’s official documentation confirms:
DCA is delivered as an MSI
It relies on Visual C++ Redistributables and internal custom actions
Installation failures should be logged and escalated to Microsoft Support
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