I am having the same problem, I was able to get to the device earlier this morning by using the IP method; 192.168.1.3 but that no longer works from either of my 2 main systems. I have not fired up the other 2. Lights shows lots of activity with the router, all 3 blue lights are on on the front panel. I have lots of space left on the drive but it does get a lot of activity. Sadly, I have not backed it up to either my WD 8TB Backup or my Seagate 5 or 8 TB backups. I downloaded WD Access and it does not find it. Quickview and Acces just offers to show the About data or exit. 1 of my main reasons for getting a mirror and not just a My Cloud single was the safety or so I thought.
I have not tried to run any AV stuff on it, it just quit today.
All that I can add is