One of my other programs made a change to poll UPNP every 10 seconds resulting in continual Notifications. Responding to the Notifications to Block didn't stop them nor did it add a new rule. So I went into Manage Rules and changed the rule there to Block, but the Notifications still kept on coming. I found the reason, I'd Allowed the program for Private only in the beginning (years ago) but now it was attempting to poll using Domain (or Public) and there was no rule created for that by Blocking the Notification. When I changed the Block rule to include all 3 (Domain. Private & Public) the Notifications stopped.