We're going to need much more detail in order to provide any useful diagnosis of what you're experiencing, but since you've mentioned 261 updates, that leads me to the following two points:
1. There's a significant distinction between updates being Needed, updates being Approved, and updates being Available for a client to install. In order for a client to install an update, the update must be Needed and Approved and Available to that client to be installed.
2. With that many updates of interest, almost certainly the majority of them are already superseded, and the WUA will not download/install a superseded update if the superseding update is approved.
Thanks for responding Lawrence. This issue is resolved via a support
ticket. A group policy was misconfigured. Now all the pcs are
communicating with WSUS server...
See you around,