COPY INTO loads files into a Delta table and remembers which files it has already processed for that target. Running the same load again normally skips those files. That is a file-ingestion guarantee, not a business-key deduplication guarantee: a new file can contain an order that appeared in an earlier file.
Aster Supply's landing directory contains updates for existing orders and one new order. Load that feed into a separate table before deciding whether to append or merge it into a business table. In this workspace the directory is a finite fixture, and its identity persists within the session. Production COPY INTO also needs permissions on the governed destination and the source storage. Use a target that matches the source schema. For larger continuous file discovery requirements, evaluate Auto Loader rather than repeatedly listing a growing directory by hand.