The issue of Edge Loop Select not working happens the most on Linux machines that use the Gnome desktop environment. The Blender hotkey for doing a loop selection in Edit mode is Alt+right-click. Unfortunately, in Gnome and a few other window managers, this key sequence pops up a menu for controlling the window.
You can fix this issue in two ways. The easiest one is to use Shift+Alt+right-click. You typically use this combination to select multiple loops, but if nothing is selected, it works exactly the same as the Alt+right-click combination.
Of course, that's a bit of a kludge. A better solution is to modify the window manager's settings and bind the function that it ties to the Alt key to another key, like the infamous “super” or Windows key that most modern keyboards have. Fortunately, this process is very simple. From the Gnome taskbar, choose SystemPreferencesWindows. You see a dialog box that allows you to change the movement key from Alt to Ctrl or Super. I recommend that you change the movement key to super because Blender also makes extensive use of the Ctrl key as well.