This will hopefully be a short post. The most likely reason the “approved” or “Declined” button is greyed out is the server you are connected to is a down stream WSUS server. What this means is that there is a WSUS server a little higher up the food chain that is dictating what updates you get /receive.
There are a couple of things that you can do:
Open Update Services MMC – OPTIONS – Update Source and Proxy Server
This will open a window that will tell you where the updates are coming from! Now if you need to specify different updates to computers that use you can uncheck “This server is a replica of the upstream server”. Once you’ve unchecked this you should be able to have a little bit more control off the updates.
I personally would just go to the upstream WSUS server listed in the “Update Source and Proxy Server” box and make the changes there.