i recommended to following this guide and compare your sources in /etc/apt/sources.list and /etc/apt/sources.list.d/*.list
https://pve.proxmox.com/wiki/Upgrade_from_5.x_to_6.0
Proxmox uses an Ubuntu kernel So every Hardware where Linux works will work with Proxmox VE.
note by default Proxmox will not verify if the device mounted ;)
Hi,
i think you missed port or http https? because if the server running on another local network machine should be work on Windows VM.
So please check IP and URL and also firewall