Home network computers aren't shown in Windows Explorer

I'm really sorry you keep getting conflicting advice. Here are a few things I know.

I am not a networking expert.

I have three computers networking on Wi-Fi through a sub modem/router hooked up to my internet provider's main modem/router that has its own built-in Wi-Fi. I choose to not use the internet providers Wi-Fi for networking my computers because it serves my wife's home-based business. 

Two of my networked computers are Win10 1803 build 17134.112, The other is a Win 7 laptop. Along with a bunch of other devices like phones and tablets and all the other stuff in the house that has internet connections.

After following all the steps in Pauli O's post and after making sure the sub-router gives the three computers the same address every time (a static address on the LAN) I can shut down all the computers and the sub-router whenever I need to. My sub-router was not the type that automatically gives a static LAN address to each device every time. I had to set that manually in that router. Now I can boot-up all the devices in any order. I can have different devices come on and off the sub-router. My Network connections and sharing between the three computers have been stable for the last two weeks.

I can also leave the Wi-Fi connection on the sub-router and connect to the main internet providers Wi-Fi connection and use the computer for business use with my wife's computers. They are all Win 7 computers. When I'm on that main Wi-Fi connection, I cannot network with my other two computers since they are on a different section. That is how it is supposed to work.

When I then leave that Wi-Fi connection and return to the Sub-router's Wi-Fi I have good solid networking connections and sharing between all three computers again.

This is my rather complicated home network. It is working well now.

Take my posting for what you will. Since I'm not an expert, it's probably worth exactly what you paid for it.

No leaving modem on is not like leaving the lights on.

Every time you turn the power off, you reset the modem settings and the connection to your ISP. Then it takes time to sync with your ISP to set your internet service up again and then your network probably is needing a reboot of all PC's on your network.

You do not need to set Static IP's. Your system and Modem from ISP is set to WAN DHCP Dynamic DNS and Dynamic IP Addressing.

Your PC adapters are set to Automatic IP Addressing for IPV4 and IPV6. Sometimes, disabling IPV6 might fix your issues.

Every time you make changes to Network, you need to reboot modem and restart all PC's. Unplugging your modem is 1/2 your problem, if not all of it.

I do this everyday for 17 years for homes and businesses. I believe you are creating your own problems here.

Here is one of my article links from my old deleted account here and more links below on it to help you with networks.

https://answers.microsoft.com/en-us/windows/forum/windows_10-networking/network-setup-for-dynamic-ip-addressing/3ed02b5e-8c83-4706-9993-7cd28bf16a88?tm=1526935286071

Most likely the setting you are looking for is in the LAN tab and perhaps in an advanced settings area. It depends on the particular model of modem/router. If you don't have a hard copy of the modem/router's manual you should be able to find it online without too much trouble.

Once you confirm that the modem/router isn't giving a different address to your computers every time you boot the router and computers, you will find your network will be much more stable.

Don't feel too bad, a lot of people (even expert users), make the mistake about setting the individual computers to a static address. And as you have seen that creates much worse problems. I'm glad you got that sorted out.

Thanks. Firstly, I wouldn't leave my modem on 24/7; that is rather like leaving a light on all the time and is a waste of electricity.

Yes, the modem is now set to get IP addresses automatically. The only way I have been told to set static addresses is by changing the IPv4 settings on each computer. But that then stops me from accessing my mobile phone's hotspot (I need to do that from time to time as my landline is 3Mbs at maximum - the phone is 30Mbs plus!).

You talk of a setting in the modem which will fix static addresses for the various computers (MAC address?). Can you tell me how to do that?

Under Advanced Setup on the modem I have:

LAN, NAT, Security, Parental Control, DNS, UPnP.

Under Wireless WI0 on the modem I have:Basic, Security, MAC Filter, Advanced and Station Info.

Are there any settings I can use so that the modem always uses the same address for each computer? That would surely enable the network to be constant each time I start up?

So, if you are getting IP addresses now automatically again then check if you are now getting always the same IP address for each PC. Login to the router web interface and check what it says. Usually, there is an option to tell the device to always assign the same IP address to the same MAC address. If you cannot assure that anything beyond this point is moot. You have to first be sure that this works.

And don't try to apply advice for different problems to the wrong problem.

Now, if you can assure you get always the same IP address for each PC: What do you want to do after this point exactly? Not just "access the other PC", please.

Don't turn off the modem/router!