Notebook threw MwcTokenValidationException error when connecting lakehouse

Hi VVT , Thank you for reaching out to the Microsoft Community Forum.

This error often occurs when the authentication token used by your notebook has expired or become invalid. To fix this, sign out of the Microsoft Fabric portal completely, then sign back in to refresh your credentials. Next, open your notebook, go to the Lakehouse explorer in the left panel, remove the current Lakehouse connection by clicking the three dots and selecting “Remove,” then re-add it by clicking “Add Lakehouse” and selecting your Lakehouse. This triggers a new authentication flow. Run a simple test query like df = spark.read.format("delta").table("<lakehouse_name>.<schema>.<table_name>") to confirm the connection. This should resolve most token-related issues.

If the token refresh doesn’t work, the issue might be due to insufficient permissions. In the Fabric portal, navigate to your workspace, click Manage Access and confirm your account has Contributor or Member permissions. Then, go to the Lakehouse, click the three dots, select Manage permissions and ensure you have read/write access to tables or files. If the notebook and Lakehouse are in different workspaces, verify you have access to both. After updating permissions, restart your notebook kernel and retry the connection. This step ensures your account is authorized to access the Lakehouse.

A misconfigured connection can also trigger this error. In your notebook, ensure the Lakehouse is set as the default by pinning it in the Lakehouse explorer. If it’s not the default, use the absolute ABFS path for queries, like df = spark.read.format("delta").load("abfss://<WorkspaceGUID>@onelake.dfs.fabric.microsoft.com/<LakehouseGUID>/Tables/<table_name>"). You can copy the ABFS path from the Lakehouse’s folder menu. If using the SQL analytics endpoint, verify the connection string in the Lakehouse settings and test it with a simple query. Restart your notebook session and test again to confirm the setup is correct.

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Thank you.