If ping tests work from VM to VM, and you don't have the Proxmox firewall configured, then there is nothing in Proxmox blocking the networking. Now you are looking at specific Windows version specific SMB & RDP capabilities. Have you installed...
Do any of your VMs still have 192.168.8.x addresses statically assigned in them?
Did you check your Proxmox firewalls? Try disabling the Proxmox firewalls.
Do you have the KVM guest tools installed in the VMs? I assume they are Windows since you...
