Note: You are currently viewing documentation for Moodle 3.1. Up-to-date documentation for the latest stable version of Moodle is probably available here: error/moodle/storedfilecannotread.
This error can occur when moving a Moodle site from one server to another and the actual file in the moodledata directory was not copied over correctly.
The entry in the database referenced a legacy resource file but the actual file did not exist on the server.
The screen reported Permissions error which is kind of correct but "file not found" would be more appropriate.