5N not connecting and not showing in dashboard

Hopefully someone may know the answer to this. My 5N is connected via a hub and all was working ok until now.
It shows in finder but will not connect. Pop up says The server may not exist or is unavailable at this time. Check the server name or IP address, check your network connection and try again.
Unfortunately it does not show up in dash board so I don’t know what the IP address is!
It also does not show up in Disk Utility

Help would be great please

I also have this problem
hope someone can know the answer to this