Check the Model Number of your unit carefully. There are many StoreJet M3 models. The model numbers all seem to END with a number (2 or 3) or a number followed by one or two letters. If the number is 2, it's an older USB2 unit. If that number is 3, its designed for the new USB3 system.
Which USB system is important, and I suspect is the root of your problem. Older laptop external drives designed for USB2 systems were built with very low-power HDD units inside so they can work with the limited power available from a USB2 port (0.5 amps). Some of these also used a special USB cable with TWO plugs on one end that had to be connected to two USB2 ports to get enough power. On newer external drive units for USB3 systems there is no such double-headed cable. Instead, they come with a USB3 cable and REQUIRE a USB3 port on the host computer. That port can supply up to 0.9 amps. Now, these latter units are sold as "compatible with USB2", BUT what that means is that you CAN plug them into a USB2 port and the data communication system will still work. However, that USB2 port will NOT provide enough power to actually run the HDD inside! The result is that the unit looks like it is working, or trying to. But it gets too many errors, or cannot actually access the drive at all.
I know about this because we ran into that with my grandson. We gave him a Transcend laptop external drive unit without realizing all this. The one we gave him WAS specified as a USB3 device, but his older laptop has only USB2 ports. When he tried to use it he seemed to write some stuff on it but all his attempts to read it back gave bad errors, and it simply could not work. When we realized the problem, we bought him an additional unit. It is a powered USB3 hub. That is, it is designed to handle 4 true USB3 (or 2) devices on its ports, and it has one USB3 cable back to the host computer for data transfer. It also has its own separate power supply module so that it CAN supply each of its ports with the full 0.9 amps that a standard USB3 port should. It does not draw ANY power from the host computer's USB port. With this system his external drive works perfectly. The drive gets enough power from the hub, and the hub and drive communicate at faster USB3 speeds. However, the connection to the laptop is via a USB2 port, so the speed of the data transfers is only at the older slower rate. Thus, although it all works this way, he will never get really fast USB3 data speeds and performance.
I suggest you have two options.
1. Do as we did - get a powered USB3 hub and use it (with its own power module) between the Transcend unit and your computer's USB2 port. It will work as above, and it can work on any computer with a USB2 port.
2. If you're only using this Transcend unit with your desktop system, you could buy and install in the desktop a card to provide a couple of true USB3 ports, then plug the Transcend unit directly into one of those ports.
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