The Network folder is not actually populated by Opus, but via the Windows shell the same as in File Explorer.
Windows in general has never been that fast or reliable at enumerating network devices, and on top of this it also seems to have a separate cache for each process, so you may see things in one list which haven't been found in the other yet (and vice versa).
Antivirus and firewalls can also play a part, by blocking one program but not another from talking to things on the network, but that would usually mean you see nothing at all, not just a partial list.
I think it may work better on networks with a proper domain/browser rather than the usual at-home ad-hoc setups, but I may be wrong. When I've been in the types of large corporate environments which have those things, the network was so slow (due to being international) and had so many thousands of machines that the Network folder had other issues. (That was before I was using Opus, and this aspect of Windows has not really changed much since.)
Something to test: Open Notepad.exe, use File > Open, and navigate that to the Network folder. Do you see similar results?
I tried your suggestion with notepad. All devices are visible.
To be honest, the native windows file manager does not exhibit the issue, Neither do two other file managers that are used occasionally here.
I would name them but I am not here to bash Directory Opus.(unless you want that information) I have been a paid supporter for many years and I will continue to be!
I can't explain that. As I say, when in the Network folder we don't have much to do with what is displayed; Opus just hosts a Windows shell window inside our main window, and the rest is down to it.
One last thing I can think of trying is:
Fully Exit Opus again.
Use File Explore to delete the the system.bin and system.off files below C:\Users\<username>\AppData\Roaming\GPSoftware\Directory Opus\Formats\
Re-launch Opus.
That will clear any saved state in folders handled via the Windows shell.