On a relatively new Dell XPS 12 9Q33 laptop with Windows 8.1, I encountered a problem I didn't think I would have with a new laptop.
My wife has a 32gb USB thumbdrive she uses for virtually everything. The drive is fairly standard - it is from Sandisk, so I reformatted it before she put anything on it, mainly because I don't like the software Sandisk puts on their thumbdrives. So fast forward a couple of years after we bought the thumbdrive. I have this new laptop I bought for work. I brought it home and my wife wanted to save some things on her flash drive. I stick the drive into one of the USB 3.0 ports (that's what it has) and it doesn't even light up.
The problem is intermittent, because sometimes the drive will work and sometimes it won't. It happens with several thumbdrives, including my fairly standard 16gb thumbdrive which has my Roboform2Go on it - the first time this happened I thought I had lost all my passwords (literally 100's of them, although luckily I had them backed up on another stick, in the cloud and on my work computer).
My first reaction was to research it on the internet. I discovered to my amazement that this is a fairly common problem with this Dell model -- so common that some forums had people saying how they had Dell replace the laptop for no cost. I called Dell and described the problem and the steps I had taken to try and resolve it. The laptop was still under warranty so they dispatched a tech to replace the motherboard.
When the tech arrived I said I was having trouble with the right shift key as well and he replaced the keyboard too. The computer now seemed to recognize the thumbdrives. A week later the problem was back. Now at least the light on the USB stick was going on. The rest of the problem was an easy fix.
You can fix it in 2 ways. The easiest way is to stick the USB thumbdrive in BEFORE you start the laptop. This always works. If you either don't want to do that, or decide after turning on the laptop that you need to insert a USB stick, you can force recognition by doing the following:
Either swipe from the right of the screen or hover the mouse in the upper right hand corner to get the magnifying glass
Click on the Magnifying glass
Type the word partition in the search box
Click on "Create and format harddisk partitions" (don't worry nothing is going to happen yet)
In the Disk Management window that comes up, resize it if needed
Right click on the USB drive in question
In the drop down menu left click on "Change Drive Letter and Paths ..."
If no letter appears in the white text area (nothing should if you can't see the drive in File Explorer), click the Add button
Click okay to assign the drive letter to the USB
The USB has now been assigned a drive letter
You should now see the USB thumbdrive in File Explorer.