The shared folder must be created by another iCloud user. You can ask someone to share an iCloud folder with you and then test again. The folder must be shared as View Only. Thank you. Giovanni

Applying this immediately after copying the file resolves the issue: var attributes = try FileManager.default.attributesOfItem(atPath: temporaryItemURL.path) attributes[FileAttributeKey.immutable] = false try FileManager.default.setAttributes(attributes, ofItemAtPath: temporaryItemURL.path) That said, it might be better to preserve the original attributes and only modify them right before deleting the file, as you demonstrated. This approach would also address the issue for files that were copied previously. Thank you for your help, Kevin!