Drive not showing up, not recognised, or a cable or port that won’t work. Most of these are fixed in a couple of minutes.
Work through these steps in order and check after each one.
If the drive powers up but your computer can’t open it, the format is usually the reason.
See Formatting your drive for Mac or PC. Formatting erases everything on the drive.
If the drive works in one port but not another, the port on the computer is the problem. If the cable is faulty, contact us: it is covered by your 24-month warranty.
This is almost always the format. A drive formatted as NTFS works fully on Windows but is read-only on a Mac; APFS works on a Mac only. exFAT, the format your drive arrives in, works on both. See Formatting your drive for Mac or PC.