Microsoft realeased KB3148812 in April, which was a buggy update. After applying it on a server were WSUS was running, the WSUS stopped working.
Microsoft withdraw the update from WSUS catalog.
Later on Microsoft released KB3159706 which was a replacement for KB3148812. But yet again after applying KB3159706, WSUS stopeed working.
Luckily this time there was few postinstall step which were necessary to resolve problems. So after installing KB3159706:
1. Run as Administrator: "C:\Program Files\Update Services\Tools\wsusutil.exe postinstall /servicing"
2. Add HTTP Activation feature: Under .NET Framework 4.5 Features in the Server Manager Add Roles and Features wizard.
3. Restart the WSUS service.