Hello!
I just tested this in my subscription and it works. I think you chose the wrong Workspace because this technology creates a separate one by default (with name [defaultWorkspace-<Your Subscription ID>-fim]) and in the tab "Change tracking and inventory | Change tracking" you need to select default workspace.
I would also like to emphasize an important point. According to these articles, the File integrity monitoring functionality will soon be greatly changed and transferred (I think including Change Tracking & Inventory, because it works via AMA now, but it will work like Defender for Endpoint agent integration later):
- https://learn.microsoft.com/en-us/azure/defender-for-cloud/upcoming-changes
- https://learn.microsoft.com/en-us/azure/defender-for-cloud/prepare-deprecation-log-analytics-mma-agent
Screenshot from this table: https://learn.microsoft.com/en-us/azure/defender-for-cloud/prepare-deprecation-log-analytics-mma-agent#feature-functionality
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