When the Windows key l is not working, it is a Windows key problem, which interferes with the shortcut combinations containing the capital letter L, e.g., locking the PC. This may occur in case some Windows accessibility settings, such as Filter Keys, have been turned on, or a gaming mode in your keyboard is blocking Windows key combinations. There are other possibilities, such as incorrectly set up driver software, registry settings preventing key combinations, and background applications that take over keyboard actions. It is possible to check these settings and make sure that there is no conflict between the software.