There can be a number of reasons why your Macbook Pro won't recognize a drive. For instance, if you have a drive mounted and your system goes to sleep, it will also power down the USB port, putting your drive to sleep. When your Mac wakes up again, the drive may not have come out of its slumber. To verify that your USB port is detecting devices, open 'Console' (Applications > Utilities > Console).

For example, I inserted a Windows (FAT16) formatted USB flash drive that doesn't mount and doesn't show on my desktop. However, in Console, you can see that it is detected and an error is generated: When you attach your USB devices, have Console running and watch to see if the device is detected and whether an error is generated. If nothing happens here (with both devices) then you have ruled out your USB devices. If they are being recognized in the system, but not showing up, you may have to disconnect them and remount them in Terminal. First, see if they are listed. Issue the command diskutil list My relevant output, again using my non-mountable USB as an example is as follows: /dev/disk4 (disk image): #: TYPE NAME SIZE IDENTIFIER 0: Apple_partition_scheme +15.6 MB disk4 1: Apple_partition_map 32.3 KB disk4s1 2: Apple_HFS True Key 15.6 MB disk4s2 /dev/disk5 (external, physical): #: TYPE NAME SIZE IDENTIFIER 0: FDisk_partition_scheme *8.0 GB disk5 1: Windows_FAT_16 2.1 GB disk5s1. First, see if it appears in Disk Utility.

If it appears but is not mounted, you can select the mount option which should mount your disk. Then, click on the Apple logo in the top left corner and select about my Mac. It should appear under storage. Also try going to the system report under the overview tab.

Media player for mac not itunes. Sometimes the lag can occur because fsck is running on it to repair any possible damage/recovery tools. People have also reported that it might not be receiving enough power if you have to plug it in. Side notes: This is commonly caused when the disk is removed without first ejecting.

Which is the best external hard disk to buy for 1 TB? My Seagate external hard disk is not detecting on any PC.What should I do now so that I can use it before going to Seagate service center? Why don't we get the whole 1 TB in a 1 TB external hard disk?

Something else to check: • Did you use the external hard disk correctly? In my situation, that was the problem! Here is what I did wrong: I turned on the external HD case's power button, and then I plugged the USB cable into my Mac. I believed that you must always have power on your devices before plugging them into the Mac. But no drive showed up! Sometimes it worked but I didn't know why.

Usually a Mac restart fixed it. I lived with this. For a long time. But today I realized that the proper method for my external drive is: • Turn OFF the external drive (if it's on). • Plug in the USB cable into the Mac. • Turn ON the external drive when the USB cable is connected.

My drive will ONLY initialize itself as a 'talking to the computer' hard drive if I have the USB cable plugged into the Mac at the exact moment that I am turning the external drive on. I'm using a two-drive USB hard disk case. And it turns out that if I start the case WITHOUT having my USB cable plugged into my Mac already, then the case enters some kind of 'clone drive A to drive B' solo-mode where it won't talk to the computer at all. So I am just adding this answer for others that have the same situation. Try plugging your USB cable in FIRST, and THEN power on the external drive.

That may be all it takes to solve it for you like it did for me! PS: Big thanks for @Allan who suggested that I look in the Console log. That was how I discovered that my USB device was detected by the computer but advertised no storage units.:) Some more fiddling later, I had realized that this particular drive enclosure's external storage mode is only activated if the Mac is already connected before powering on the drive.