Have you got worried because the MacBook Pro does not detect SSD ? The MacBook pro supports the SSD type hard drive which is different from regular drives that consists of plates and motor. The whole drive is made up of circuits so your can say it a giant memory card that has excellent performance. You attached a previously used or a completely new SSD in you MacBook Pro but you discovered that the MacBook Pro does not detect SSD. You might be first thinking of any data that is stored in the drive, you should first check it by connecting it to some other system. If the problem is still showing then it is confirmed that your drive is damaged or corrupted. The SSD also uses the file system and if it is corrupted the drive becomes inaccessible. You can fix this by formatting and if you have lost any data while fixing it try using the time machine backup or the Mac data recovery software. The later option should only be chosen when the time machine does not work. The software provides complete recovery without much fuss. So download software when MacBook Pro does not detect SSD issue is dealt.