I notice that a file has appeared on all 3 computers, alongside the files I am trying to tag:
"XYplorerTag.dat"
The data this file contains is the tag being replicated to all machines.
So ironically the tag that is not being replicated is the one which was created on the server MATTHEW-PC and is held where tags should be held, i.e., in the folder designated for it.
The tag that IS being replicated is held somewhere else (as above) where it shouldn't be held, and has a name I didn't give it.
Image:
https://imgur.com/a/FnrHll0
Experimenting, I can now get tags to replicate across to all machines, but not by doing what the Help file tells me to do.
[1] First on MATTHEW-PC I create a new tag alongside a file
[2] I export the tag from MATTHEW-PC by clicking "Export Local Tags"
[3] I then import it to another machine clicking "Import Local Tags" on that other machine
[4] The same process works when creating tags on the 2 'client' laptops and replicating them to the server (and to each other)
The data relating to these successfully replicated tags is held in the file "XYplorerTag.dat" just mentioned.
Nice.
But not orthodox, and not automatic.
To misquote Startreck: "Its life, Captain, but not as we know it".