"Internal Error" when using SQL DB connection in Lookup/Copy Activity as guest user

Thanks for sharing this finding—it could definitely save others some troubleshooting time.

Based on your description, this appears to be related to guest user permissions or a current Fabric limitation rather than an issue with the Lookup or Copy activity itself. The fact that the same SQL Database connection works correctly when created by a native tenant user, but returns an "Internal Error" only for guest users, points to a service-side authentication or authorization issue.

A few suggestions:

• Verify that the guest account has all required permissions on both the Fabric workspace and the SQL Database.

• Test by recreating the connection using a native tenant account (as you've already done) to confirm the behavior.

• If the issue persists consistently for guest users, consider opening a Microsoft Support ticket, as this may be an undocumented product limitation or bug.

If you receive confirmation from Microsoft or discover a workaround, please share it here to help others experiencing the same issue.

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