My four airtight outdoor cameras have been working great on my LAN but suddenly, on by one the have disappeared from the ip camera tool. Interestingly, though they did not appear on the camera tool, I was able to view them by entering the ip address but then, one by one they have become unavailable. I had made no changes to settings so am pretty curious what has happened. My router shows the on line, but obviously the are not. Ideas? Thanks