If you check your licenses in SIM on the Notification Server, are any expired or exceeded? This would cause the problem you're describing.
Additionally, to push a software package using a Software Quick Delivery task, the Software Management Solution plug-in must be installed. Is this plug-in installed? If not, you may need to enable it at Settings > All Settings, then select Settings > Agents/Plug-ins > Software > Software Management > Software Management Solution Plug-in Install policy.