A fix which worked for me was:

1) Click start
2) Click run
3) Type cmd and click ok
4) Type: net stop wuauserv 
5) Press enter
6) Type: Del “c:\windows\windows update.log”
7) Press enter
8.) Type: net start wuauserv
9) Press enter
10) Type: wuauclt.exe /resetauthorization /detectnow
11) Press enter
12) Wait for upto 10 minutes. Machine should start to check in