Since 4.8.3 it work again

I'm actually very comfortable with veyon, so I wanted to know why the PC appears in red (authentication failed or access denied).

From what I see and can perceive, Veyon is used more in Windows than Linux (Ubuntu, Debian) in classrooms and not Linux in classrooms.

My issue is similar - the screen refresh is slow enough to watch it crawl down the screen. That's when connecting to a variety of different systems. Other means of connecting to them - Dameware, RDP, etc - act normally.

I am facing the exact same problem. Did you manage to find any solution?

example: there is a window asking for a password. The window is open and active on all stations.

@ARoger It doesn't work

Go to Veyon Configurator, Locations, and Computers, Go to your Computer list and look for a + icon in the right box, now add it like the other ones you did, and you should be fine.