Did you upgrade from Windows 7 to Windows 10 on your Latitude E7440? Is your wireless stuck in “Airplane Mode”? Does clicking the thing to disable airplane mode just flash at you when you click it?
If so, you need to open Device Manager and disable the “Airplane Mode Switch Collection” device under Human Interface Devices. After that, you should be able to turn airplane mode off and wifi back on. How annoying.
Update for Windows 1709 (Fall Creators Update): You need to reboot after disabling the “Airplane Mode Switch Collection” device, then wifi should start working again.