I have the same issue, when I'm not launching Master without admin rights, I'm told that I don't have access to this network. Launch with administrator rights - just fine. Using LDAP and LDAP tests for access are all OK.
Simply pick a computer (yours maybe) that will be the lead "Master" and install the appropriate version per your OS (32bit/64bit) using all the default settings. Run the same installer on every client/student computer but uncheck the box Veyon Master box during install. Take not of the computer's name and the MAC number. They all need to be able to communicate so it's ideal if they're all on the same domain.
On the Master computer, open Veyon Configurator and click Locations & Computers. If you have multiple locations, like many buildings on a college campus, you create locations on the left side, like you may use folders in File Explorer. On the right side you add the client computers for each location. Click apply and you're done.
There are other security settings, LDAP settings and things you can adjust as needed for your environment.
In fact, it seems commands like C:\Program Files\Veyon\veyon-service.exe restart have absolutly no effect.
I tried with service stop (and server too) on the client, and it changes anything in veyon master : the client is still here and responding.
The connection notification goes away if the end user clicks the OK/close button.
On the previous version of Veyon which I did my initial tests on - the connection notification would reappear if the pupil clicked the OK/close button on the notification.
Gah! Ignore me.. That didn't work.
I'd mistakenly unticked the "show notification when an unathorized.." box
I'm just going to roll with it for now.
I'd still like to know how to stop it remembering my previously connected clients, though. At the moment, it looks like I'm going to have to replace the shortcut for Master with a script which deletes the per-user settings file and then runs Master.. Not ideal.