Well, after the forehead smacking moment when Tom kindly reminded me of the need for an '*' on Key Attribute, I tried it and it still did not work.
In fact, from the description in the User Guide, the '*' is only needed if you are matching on an Attribute other than .ID.
If you are matching on .ID then Aware should (and does) recognise the column and does Update the correct data.
However, after 6 hours of frigging with this I have discovered the problem.
My import csv file on Mac was the problem. When I constructed the csv file only on Windows it worked.
Here is the start of the csv file in hex on Mac....


Notice the first 3 characters EF BB BF
They are invisible in both Brackets and Sublime on a Mac
When I constructed the csv on Windows it looked like this....

At the end of the day, I still don't know where these 3 characters came from. Excel's csv export? Sublime? Brackets? or Mac file system....Would be interested to know but not going
to waste any more time on it.
Bottom line is... if you ever get an import error that says something like First Column Name must start with Employee for the column Employee.ID .......
This could well be the problem... hidden character in the start of the file.