These are all Windows 10 systems, the IP addresses are assigned dynamically, and all are assigned the same workgroup name.. This problem of not seeing some computers on the File Explorer network list started when the "original" Creators Update came out last spring. I had no problem before that. There are many posts across the net mentioning this issue and Microsoft has done nothing to fix it yet. Usually the first computer that is turned on gets assigned as the "master browser". It keeps tabs on any computers that come on later. If that first system is shut down, the next system is supposed to take over as the master browser. Somehow this is not happening properly. From what I have experienced, it seems that if the master browser computer goes into sleep mode and the second computer picks up the active systems, when the first system comes back on line, the second computer may not pick this up. If have seen at times that a computer is not even listed in its own Network list. There is usually one workaround where you enter the nae of the computer (\\<computer name>) on the address line of the Network section of File Explorer and it then gets picked up.
I normally do not leave my systems on all the time. There is another workaround using a router which some people have used with great success because the router is always on. They plug a USB flash drive in the router and set the router up as the master browser. This is why I am interested in getting my 880L set up as the master browser.
JohnD