t_viewing_pptp_logs
Go to Network > User VPN > PPTP VPN > Troubleshooting.
See also:
Point-to-Point Tunneling Protocol (PPTP) VPN
Enabling PPTP VPN
Configuring General PPTP VPN Settings
Viewing PPTP VPN Clients
Advanced Settings: Enabling Debug Mode and Encryption Level
Troubleshooting PPTP VPN