Change the USB cord or USB port to test if they are worn.Push the USB cord into the USB port hard to make sure it is connected properly and firmly.Solution 3: Format the external hard drive to make it workableīelieve it or not, the very first step for troubleshooting the problem is to check if there is a poor or even broken connection between the external hard drive and the Mac.Solution 2: Run First Aid to fix the disk errors.
