The old problems have, for some reason, resurfaced.
Some days ago, having an afternoon free, I decided to (simply) network my 2 “new” PCs and their associated hardware.
After a bit of service adjustment, permissions-granting and re-booting, both PCs “saw” each other and were happy to “handshake”. I transferred multiple large files with no problem.
The next morning … each PC was invisible to the other. All the settings were as should be so, again, I reverted to manual transfer of large files.
Yesterday day afternoon, while waiting for an unrelated process to finish, I googled “Windows 10 missing pcs on network” and some slightly different information was available:
https://www.surfacetablethelp.com/2018/02/computer-browser-service-missing-and-not-working-after-windows-10-fall-creators-update.html
Computer Browser Service Missing and not working after Windows 10 fall creators update
More searching revealed that:
Windows 10 version 1803 has SMB 1.0 disabled by default. The computer browser service is a legacy service which was part of the old SMB 1.0 file sharing system. If SMB 1.0 is disabled there is no computer browser service.
So, for both PCs, I followed the advice in the original article:
For security reason the Windows 10 fall creators update has disabled the SMB1 feature. If you need to use SMB for sharing files and printers, try the method to restore and turn it on again.
How to fix Computer Browser Service Missing and not working after Windows 10 fall creators update
- Type Control Panel in Start menu from your desktop, and open it from mathed result.
- Navigate to the Programs & Features > Turn Windows features on or off.
- Locate the “SMB 1.0/CIFS File Sharing Support”, check the checkbox associated with it and press OK button. Then restart the system to take effect.
LO and behold - each PC could “see” the other … but what will tomorrow bring … 
