Hi! The 403 error you're seeing is almost certainly not coming from SharePoint — it's coming from Azure Storage.

The key clue is in the error detail: access denied to /cas cloud path. The /cas path is Unity Catalog's managed storage location (Catalog Asset Store) on ADLS Gen2. Lakeflow Connect spins up a job cluster that tries to write there, and that cluster's identity is being denied by Azure.

Here are the three things to check, in order of likelihood:

1. Missing IAM role on the UC managed storage account (most common):

The Databricks workspace managed identity needs Storage Blob Data Contributor on the ADLS Gen2 storage account that backs your Unity Catalog metastore. Go to: Azure Portal → Storage Account (the one linked to your UC metastore) → Access Control (IAM) → check that the Databricks managed identity has Storage Blob Data Contributor.

2. Missing Unity Catalog privileges on the destination:

 The user or service principal that created the pipeline needs explicit grants on the target schema

GRANT USE CATALOG ON CATALOG <your_catalog> TO <principal>;
GRANT USE SCHEMA ON SCHEMA <your_catalog>.<your_schema> TO <principal>;
GRANT CREATE TABLE ON SCHEMA <your_catalog>.<your_schema> TO <principal>;

3. Missing Microsoft Graph API permissions on the Azure AD app:

 If the above are fine, check that your app registration has admin consent granted for Sites.Read.All (or Files.ReadWrite.All) under Microsoft Graph API permissions in Azure AD — without admin consent the token is issued but scoped incorrectly.

Why option A is probably it: The error fires during pipeline compute resource setup, before it even touches SharePoint. That timing means the cluster can't reach UC storage — the SharePoint credentials aren't even in play yet at that stage.

Hope this helps!