Alas - I spoke too soon...
Although I reported that I was able to connect to the DiNi (both in TBC v2023.10 and Trimble Data Transfer) - I did not actually advance to download a level file. When doing his next step, the 'transfer" starts but never finishes. The wee 'receiving' window is open and it implies a data transfer is happening, but the progress line does not advance.
So the connection problems continue, and I have only progressed one stage with the problem. If I mange to stumble across a fix I will return to this thread to post a report....
I am astounded that Trimble don't seem to worry/care/bother about this issue.