Network PCs not showing

[#1]

I have 3 PC systems, 2 laptops and 1 desktop.  They all run Windows 10 v1909.

I have issues with them all showing in each other network explorer window.

Laptop 1 can see all 3 systems, and also it sees the router as a PC as well. It also sees all the multi function devices normally.

The Laptop 2 can see itself and the desktop, and again the multi function devices.  It however shows the router as a multimedia device.

Desktop can see Laptop 2 but not laptop 1, and again the same with multi function devices and router.

I have search on the internet, and found loads of potential solutions, none work.  I already check the function discovery services are started, and other as noted by a posted solution.  Sharing options are all set exactly the same on all systems.  They are all on a private network, and under the same workgroup.  I have double checked everythig I can think of, and all systems sharing settings and services are set identically.

Oddly enough, on all systems, I can ping them by IP and device name absolutely fine. I can also connect to them by entering the address in the explorer address bar as \\Device Name\ and all shared resources show normally.  Its just they PCs refuse to show up in the network explorer window.  I have attached a picture of the laptop that shows everything.

I have tried everything I can think off, even enabling SMB V1.

Its just a faff, and i like things to just 'work', but I think i am resigned to the fact windows networking out of a Domain environment is just not very good and a bit buggy.  I may just have to resort to typing the hostname in the address bar if I want to connect....

As a thought, and not sure if it makes any odds, the Laptop and Desktop that just see each other, and not Laptop 1, are all clean installs of V1903, upgraded to 1909 via disk.  Laptop 1 is a much older windows 7 system, upgraded to 10 V1607 and incrementally to the other versions via either disk or windows update. Could it be just corrupt OS components causing Laptop 1 not to be seen by other systems, even thought it can see them all......  (Laptop 1 in the image is Dad-Laptop)

[#2]

I would compare firewall settings (advanced firewall settings) and also if any folders are shared. IPC$ should be enabled as default.

The Plusnet router will probably be showing as a PC as it has USB drive sharing capabilities, ie SMB sharing

[#3]

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@MMG wrote:
The Plusnet router will probably be showing as a PC as it has USB drive sharing capabilities, ie SMB sharing

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On Win7 it is clearly identified as a router / gateway.

Further it advertises itself on the network via UPnP - the services it offers are advertised too. If you download an android app called "Network Analyzer" it will let you scan the network and then see the UPnP properties of devices it finds.

[#4]

Thanks for the replies. I will look into the firewall, but I've never messed with it, and should be at default settings. The only shares on all systems are the default public folder shares. I could try creating a new share on each machine, to see if it's a public folder sharing issue I suppose, but each pc dosnt see each other so I doubt that it will help...