Sometimes these switches get moved to the locked position by accident, so have a look for a switch on your drive / card and make sure it isn't in the lock position.
Some USB drives and SD cards (but not microSD) have physical switches which let you 'lock' the drive to stop any files being accidentally overwritten or wiped. If you're having trouble copying a file to a drive in Windows, can't delete files or are facing an action camera or dash cam that's refusing to work with a microSD card, it could be that the storage is write protected.
