Hello. What model is your hard disk? Have you tried connecting this hard disk to a MAC computer? Is the connection successful? Any more error messages? What is the current format of mobile hard disk? As far as I know, different operating systems use different hard disk formats. If you want to copy the files of Mac system to the hard disk, you must ensure that the hard disk is in HFS+ or FAT32 format. Windows computer: NTFS MAC computer: HFS+windows and MAC computer can be used on both sides: If FAT32 format is wrong, the hard disk may be unreadable. If you want to reformat, remember to back up the information first to avoid losing it. I hope this information can help you.