Before you even open your first menu, give two quiet minutes to paying attention to this drive. Plug it in, have a look at the LED light. Put a finger lightly on the casing and see if you can tell whether the motor spins up. Listen. If it's silent and powering on evenly then that is very different from a drive that stays completely dead, and still much different again from one that has started making some new noise it never used to. These observations will group 'not showing up' into its three actual categories: a cheap connection problem, a file system problem that's fixable with care, or a hardware problem (one for the lab).
Do you hear sounds coming from your disk like clicking, buzzing, beeping, or a spin-up that keeps stalling and restarting? If so, don't go any further. Those are mechanical problems, which are usually due to crashed read/write heads and/or a seized motor, and dropped/knocked drives are the common cause. A drive in this condition, if left powered, could grind away at the physical platters where your files reside. Disconnect the drive and jump directly to the last section.
Begin by looking at the cable. The thin leads that come bundled with portable drives are a known weak point, and Seagate and WD units get through them at a remarkable rate. Then move to another port, directly into your computer itself, and avoid using a hub or any type of port on the front panel of the machine. If you have a second computer handy, try it on that as well. Mains-powered desktop drives add one more suspect, the external power supply, as these can also fail. A desktop unit that will not spin at all could potentially just be due to a dead power adapter; therefore try a compatible spare adapter before assuming the disk has failed.
On Windows, open Disk Management (right click the Start button). A drive that you see in Disk Management, yet can't find using File Explorer, has often just lost its drive letter, and changing it back via 'Change Drive Letter and Paths' is safe. If your disk displays as RAW or 'unallocated', or if Windows prompts you to initialise the disk, then the file system has corrupted. In most cases, your files will be still intact below this layer of corruption. Decline all three of the format, initialise and 'repair' options, as they will write new data on top of the existing structures that a recovery would be rebuilt from.
On a Mac, the first step is to run Disk Utility, then toggle View → Show All Devices. It is common for the hardware to be shown in Disk Utility while its volume fails to mount when you try. There are two mistakes to avoid here: Erasing (destructive by definition), and running First Aid on a disk that sounds unwell (which pushes failing hardware harder). A benign case to rule out would be if you have a Windows-formatted disk that mounts poorly on your Mac or if you have a Mac-formatted disk that mounts poorly on a Windows computer. In both cases the data remains intact; however it requires reading the data using the platform it was formatted with.
A Seagate portable with its LED lit but nothing showing on screen (and a completely normal sound) very often indicates either a failed USB bridge board or corrupted firmware. While the data should be good, the path to getting at the data will require something other than a new cable. On newer WD My Passport and Elements portable drives, avoid one common trick for accessing your data altogether: simply removing the disk from its case. All of these newer drives have their encryption done in hardware on the USB board, so when you remove the drive from its case and place it into another caddy, all that appears is jumbled gibberish. Proper recovery reads through, or works around, that original bridge board.
End the plug-in-and-hope cycle here. No matter what brand your drive is, if it shows up to you once in five times (and then just once in ten), it is on a failure curve, and each "retry" consumes a little bit of the remaining life of the hardware.
Draw the line here: any clicking, beeping or history of being dropped; a RAW prompt (or "initialise") over files that you actually need; detection that comes and goes, trending worse; or recovery software which has already been churning for hours with no results. Beyond this line further experiments will only burn through the data, while establishing the true fault costs you nothing at all.
First get a quote for your data recovery, then wrap your external hard drive in bubble wrap, while it is still in its enclosure. Include the drive's cable and power supply as well. Then send it by post using tracked delivery (or drop it off at our lab in Bristol, Monday to Friday, 9am to 5:30pm, with no appointment needed). Within 2 working days of your drive reaching the lab we will diagnose it and report back to you with a clear picture of what can be recovered from it, along with one fixed quote for you to accept or turn down. If you'd like to learn more about this service please refer to our external hard drive recovery page, or if you'd prefer to start with the free online diagnostic please go there first.
One rule above all: any drive that matters that has started to click, buzz or beep should be shut off and remain shut off. Running time never improves a mechanical failure; it only spreads.
We offer a free diagnostic on arrival, one fixed quote, and on logical faults, in most cases you only pay if we recover your data. Please begin online or call us using our freephone number.