Check the permissions side first. A 403 usually points to an authorization issue rather than the cluster itself. Make sure the pipeline’s service principal/user has the required Unity Catalog privileges on the target catalog, schema, and tables, and also verify the storage credentials/external locations if you’re using them. If those look correct, then move on to checking network rules or workspace connectivity for the ingestion cluster. The pipeline cluster is managed by Lakeflow, so cluster-level access is usually less likely unless there are custom policies in place.