Hi BM if your VPN is IPsec, then you might want to examine charon's output via journalctl. Probably openvpn, wireguard and others can be found there, too.
Another thing to try is to establish the VPN connection using nmcli in a
terminal window, e.g.
nmcli con up "VPN name"
Maybe you get a usable error message this way.
Regards
Harri
