FWIW - now I can’t connect over the LAN …oh the irony 
was working on earlier versions - can’t connect with a mac or win10 performer. They can see the studio PC but can’t connect - “connection error: local connection failed” - leaves the performer app in a slightly unstable state.
“They can see the studio PC” - how do you determine that? Is the blue LAN button lit?
yes - and it shows the correct IP as usual - just doesn’t connect - gives an error as described
also randomly gave another “incompatible version” error - they are all on 4.0.42.240 - then it wrote that on the bottom of the screen where it normally says “connected to Musi”
attempting to connect on a Mac client (4.0.42.240) over the LAN didn’t work either - fell over rather spectacularly with a crash on the performer side (and a dump - which I didn’t save !)
was all working fine last time I tried - a few versions ago.
also - still getting useful work done - another (mainly) positive session earlier
thanks 
Confusing. We definately didn’t change any of the local connect stuff as it worked fine (and still does over here with all our tests). What’s weird is that it shows the address. If it crashes again pls save the report, thanks.
I’ll see if I can get a crash log tomorrow
sent
SOLVED!!!
The machine running VST Connect had several network connections enabled, including VirtualBox and VMware adapters. I disabled all the adapters except the active one connecting to my network. The Lan indicator on the ‘remote’ machine running Performer immediately illuminated and I was able to connect.
I am guessing that the UDP broadcasts were being sent on an unused network which explains why I couldn’t see them on Wireshark. The clue came from a google search on ‘Win 10 UDP braodcast’.
It has taken me weeks and much hair pulling to find this so I hope it helps somebody else.
Now to get on with the testing and learn how to use the system!
Alan
good detective work
Absolutely! Thanks for finding this. VST Connect grabs hold of the first available adapter, which is the ‘right’ one in 99% of all cases. Sorry for you to have to find out the hard way, and kudos for solving it.
Just to close out this thread - I spent some time playing with the system on my LAN, learning how to drive it and learning what could cause it to glitch; mail, cloud storage syncing etc, etc. Then earlier today I ran a live remote session with a player who had never used it before. It worked perfectly.
This is a game changer for me.
Thanks!