Databricks intentionally stops existing streaming reads and writes after an external Delta table is converted to a Unity Catalog managed table. This protects data consistency because the table's managed storage location and access path have changed. The documented recovery action is to restart the stream with the same configuration. The existing checkpoint can then resume processing from the last committed offset, and supported path-based access is redirected to the converted managed table. REFRESH TABLE invalidates cached metadata but does not repair a stopped Structured Streaming query or modify its checkpoint. Deleting the checkpoint would discard progress information and could cause unnecessary reprocessing or duplicate output. Additional permissions are not the indicated solution when the failure is specifically caused by managed-table conversion. Therefore, option A is correct.