iMac/Finder Won't Display Network Devices

Vexing problem, here, but hopefully one with a simple solution:

I have a home network with Airport/Time Capsule that serves an iMac, a MacBook Pro, and a Mac Mini music server. Normally, I can see all devices in the Finder sidebar, and it has rarely had an issue. My main cross-network activity is to Share Screen of the Mac Mini from either the iMac or the MacBook Pro, i.e., controlling the headless Mini music server from other computers.

Starting last night, the iMac's Finder fails to show either the Mac Mini or the MacBook. Under Devices, it shows the 1TB disk in the iMac, but that's it.

The MacBook Pro's Finder shows all expected devices... the Mini, the iMac, etc.

Using Finder's Go, I can Connect to Server to the Mini (but I need to Share Screen), so the iMac can connect to Mini, but still no display of the Mini in Devices on the sidebar. I should also be seeing the Airport's disk under devices, but it's not there.

In Finder preferences, all boxes are checked for display. In the Sidebar preferences, I see the following, which (perhaps also) doesn't show the Mac Mini, the MacBook, or the Airport disk.

Any ideas?

Thanks!

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