Since August 2015 Microsoft tucked deprecated (replaced with something else because) wuapp.exe and enclosed the functionality withing the windows system settings app. To check for updates now, select the Start
Windows logo Start button
button and then go to Settings
Gear-shaped Settings icon
> Update & security
Circular arrows Sync icon
> Windows Update, and select Check for updates. If Windows Update says your PC is up to date, you have all the updates that are currently available

Note: If not all desired updates are applied, the settings by default only apply updates for the core operating system. All other functionality must be requested by going to:
On the Microsoft Update site, click Change Settings.
Scroll down the page, click to select the Disable Microsoft Update software and let me use Windows Update only check box, and then click Apply changes now.