Normally this problems appear when your registry has been changed by some malware or spyware to keep your computer unsafe.

if your computer doesn’t show windows update setting, and a yellow error message says, “Some settings are managed by your system administrator. then following solution may resolve your issue.

Windows update has been disabled by your system administrator

How to do it manually

1. press window key + R
2. Regedit and hit enter
3. Search for the following key

HKEY_LOCAL_MACHINESOFTWAREPoliciesMicrosoftWindowsWindowsUpdate

4. Then on right side pan look for the key

DisableWindowsUpdateAccess

5. if this doesn’t exist, create one by right clicking and chose dword value, 32/64 bit as per your OS.
6. rename this key with this name ( DisableWindowsUpdateAccess)
7. then right click on this dword key, select modify
8. Enter this value

00000001

9. Restart your computer, and your updates settings will be back

Automatic Registry Patch

if you cannot go through all this lengthy process simple click the following link to download registry patch, unzip it and double click it to merge it, Restart computer & you are done.
Registry Patch Download Link

Note: This solution only works on windows 8/8.1/7/XP