network works on some computers and not others and bounces around

I volunteer for a ministry in Memphis Tn. We have a wdmycloudmirror that is used so the staff can access and store files on the network and be able to use it from any computer in the building. It has become a problem recently that the network works on some computers and is entirely \\wdmycloudmirror unfindable and 0 pings returned from the command prompt. Come in the next day and works on the computer it didn’t work on but the computer it was working on stopped working. I have no idea why this is happening. Why does it bounce around and seemingly just decide I don’t want to work on this computer today?