Mac reports "Downlevel TV-Quick Support" in error

Today I tried to connect to a friend's Mac which is running MacOS 10.9 Mavericks.
I talked her through downloading the Tv.QS from the web page and then talked her through starting up the App.  Partner ID appeared and was handed over.

When I try to connect I get the pop-up stating that the User is running a downlevel version of TvQS and should upgrade.  I'm running Tv 15.4.8332 on a WIndoze 10 platform.

I next tried to connect to my daughter's Mac running MacOS 10.14: Mojave (again getting her to download TvQS as hers is a virgin 4 day old laptop ! Ok for some) and this worked fine.

Does anybody have any previous experiance of this?
I've trawled through the various forums and blogs but can't find anything similar.

Thanks in advance.
Phaz