Network missing in Finder, can't connect to external drive

Go to Finder > Settings... > Sidebar and click a check mark in Bonjour computers and Connected servers.

Note- in Catalina this will be Finder > Preferences... > Sidebar.

sapper wrote:

I am unabl to estore Network to the Finder side bar since Monday when I lost my internet connection.

Exactly how did you lose your internet connection? What changed?

You may have to reset the router and both computers.

• Shut down all three devices.

• Disconnect the internet feed from the back of the router. Wait two minutes then reconnect.

• Restart the router. Watch the status lights and let the router stabilize its internet connection.

• Restart each Mac and make sure it reconnects to your wi-fi.

• Check if your Network devices populate properly in the sidebar.

Sorry, but that was of no use whatsoever. See below: as you can see, I have External Disks and Bonjour computers and Connected Servers checked.

It was a start. None of the peer volunteers here can look over your shoulder and see what's what on your Mac. We rely on you to paint us a vivid picture with words and graphics.

Under normal circumstances, does each computer see the other in the sidebar, or is only one Mac supposed to display on the other?

No need to disconnect the internet cable from the wall, just from the back of the router. And that is not necessarily required, but in some instances it can be helpful. If you're unable to do that, then don't worry about it.

Check the Network settings on each Mac to ensure that it has reconnected to your home network. I've been assuming these computers are connected by wi-fi, but maybe you're using wired Ethernet for one or both?

Set up file sharing on Mac - Apple Support

Because sharing was interrupted, you may also have to turn off file sharing and then turn it back on again.