Cannot connect to LAN game

I am a network system administrator and I play Minecraft with my 2 children. previously before 1.19.63 our LAN game worked without any problems. Although nothing has changed on my network I have been through all the usual troubleshooting, all network sharing is on and firewall and AV has been turned off. I have even removed and reinstalled Minecraft on 2 machines and reset the network stack on all 3 machines. I have also created new test worlds on all 3 machines and on each machine that runs the test world the other 2 cannot see the world. I am at a loss as to where to turn now. The only change to any of the PC's on my network is my sons machine having the epic games launcher installed? No add-ons in use either.