Home network computers aren't shown in Windows Explorer

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

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.

Thanks,

I go ipconfig /all on my computer and it gives me four different physical addresses of the form 24-0A-64-B0-32-85 (that one is under 'Wireless LAN adapter Wi Fi)

I go to my router's LAN settings and "Add entries" under 'Enable DHCP Server" and put in that MAC address with an IP address of 192.168.0.3 (the current IP address) and it says that is an 'invalid MAC address'. It says that for all four of the physical addresses.

Am I doing something wrong?

Reading those last postings I realize that I have wrongly understand that you have to set IP's to static because that is required by your mobile hotspot, which lead me to wrong track.

Sorry for that miss understanding.

In some users (like myself) keeping router on pure DHCP and disabling IPv6 has been helped, but I see form previous postings that you have already try that(?).

There should be some kind of table on your router (DHCP) settings like I have on my old router. By clicking button "Manual Assignment" that router remember which IP-address belong to each MAC address. (Even while this IPv6 trick work for me  didn't put my router back to full automatic and that's just laziness.)

New routers / modems may remember this automatic and no changed required.

Have you look your router manual for IP-assignment?

Which is branch and model of your router?