It doesn’t happen too often, but I find myself requiring this script from time to time:

net stop wuauserv
REG DELETE “HKLM\Software\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update” /v LastWaitTimeout /f
REG DELETE “HKLM\Software\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update” /v DetectionStartTime /f
Reg Delete “HKLM\Software\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update” /v NextDetectionTime /f
net start wuauserv
wuauclt /detectnow

Or just open a command prompt and type
wuauclt /detectnow and see if that works.