Most probably your VPN is failing and therefore you don’t have internet connection. It could happen that NordVPN disconnects. Just search the web, you will find a lot of entries on this. Maybe you should connect to this forum post. It’s a request how to automatically reconnect to NordVPN.
https://dietpi.com/forum/t/auto-reconnect-for-vpn-dietpi-nordvpn/4266/1