Error Code 800B0001

1. On the WSUS server, install the KB article KB2720211. OR 
2. Select the option to install the updates online from Microsoft and check if you are able to see available updates for your system. You should be able to see the updates now. 
3. Also check if the “Windows Internal Database service” is running on the WSUS server. If not then try to start it. This service should be Automatic. 

How to check the WSUS server from client : 

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate 

You should see the keys WUServer and WUStatusServer which should have the locations of the specific servers.