@Tom-Elliott
Automatic snap-ins (connected to the group or the PC) don’t always work well, e.g., when the PC is busy with itself and the Microsoft ecosystem after cloning. For example: the PC isn’t ready for the snap-in yet because it’s currently installing an update, isn’t in the domain yet, etc.
That’s why, over the years, I’ve gotten into the habit of first checking whether the PC is in the domain, letting it boot up completely, and only then running my “one” snap-in per PC. In that single Snap-in, I gather everything I need to set up the PC: for example, a student PC needs a Veyon client, the student proxy server, etc. => Student Snap-in; a teacher PC needs the Veyon Master and the fast teacher proxy => a separate Snap-in for teacher PCs

@Tom-Elliott yes, I checked the services, they all running.
systemctl status nfs-server
● nfs-server.service - NFS server and services
Loaded: loaded (/usr/lib/systemd/system/nfs-server.service; enabled; preset: enabled)
Drop-In: /run/systemd/generator/nfs-server.service.d
└─order-with-mounts.conf
Active: active (exited) since Tue 2026-06-30 09:06:50 UTC; 17h ago
Process: 4995 ExecStartPre=/usr/sbin/exportfs -r (code=exited, status=0/SUCCESS)
Process: 4997 ExecStart=/usr/sbin/rpc.nfsd (code=exited, status=0/SUCCESS)
Main PID: 4997 (code=exited, status=0/SUCCESS)
CPU: 10ms

Jun 30 09:06:49 fog-svr.local systemd[1]: Starting nfs-server.service - NFS server and services…
Jun 30 09:06:50 fog-svr.local systemd[1]: Finished nfs-server.service - NFS server and services.

rpcinfo -p 192.168.13.99
192.168.13.99 mountd
rpcinfo -t 192.168.13.99 nfs
rpcin program vers proto port service
100000 4 tcp 111 portmapper
100000 3 tcp 111 portmapper
100000 2 tcp 111 portmapper
100000 4 udp 111 portmapper
100000 3 udp 111 portmapper
100000 2 udp 111 portmapper
100024 1 udp 50174 status
100024 1 tcp 34667 status
100005 1 tcp 20048 mountd
100005 2 tcp 20048 mountd
100005 3 tcp 20048 mountd
100003 3 tcp 2049 nfs
100227 3 tcp 2049 nfs_acl
100021 1 udp 38178 nlockmgr
100021 3 udp 38178 nlockmgr
100021 4 udp 38178 nlockmgr
100021 1 tcp 37227 nlockmgr
100021 3 tcp 37227 nlockmgr
100021 4 tcp 37227 nlockmgr

I deployed the image using a VM on Proxmox and it worked, but with a phisical PC it gives the error like above. All are on the same VLAN.

@Tom-Elliott awesome, thank you!