My computer isn't listed under network computers

[WNathanson]

My computer is not listed either in the dropdown Network list, nor as a network computer under the network link on the control panel. This computer has an Ethernet connection. My other machine (also Windows 10) is listed and accessible (through the internet, I guess).
However, though this second machine is listed in my homegroup, when I click on it I am told it is not available. I am at a loss