Failed Update Licenses via Proxy Server

Hi Guys,

I want to updating fortigate 501E licenses through proxy server. I've configured autoupdate tunneling to proxy server and override fortiguard server with IPv4, but it still failed to update. Here is the configuration autoupdate tunneling on the fortigate :

config system autoupdate tunneling  set address 10.11.25.218  set port 3128  set status enable

and here is the logs error that I've got :

DC-SETU-FWSVRFARM-01 (global) # do_setup[239]-Starting SETUP upd_cfg_get_host_by_name[95]-Failed to gethostbyname for update.fortiguard.net upd_act_setup_with_action[191]-Trying FDS 173.243.138.68:8890 tcp_connect_fds[173]-Proxy tunneling enabled to 10.11.25.218:3128 negotiate_proxy_tunnel[116]-Error reading upd_comm_connect_fds[423]-Failed TCP connect upd_act_setup_with_action[195]-Failed connecting to 173.243.138.68:8890 upd_act_setup_with_action[191]-Trying FDS 96.45.33.89:8890 tcp_connect_fds[173]-Proxy tunneling enabled to 10.11.25.218:3128 negotiate_proxy_tunnel[116]-Error reading upd_comm_connect_fds[423]-Failed TCP connect upd_act_setup_with_action[195]-Failed connecting to 96.45.33.89:8890 upd_act_setup_with_action[191]-Trying FDS 173.243.138.66:8890 tcp_connect_fds[173]-Proxy tunneling enabled to 10.11.25.218:3128 negotiate_proxy_tunnel[116]-Error reading upd_comm_connect_fds[423]-Failed TCP connect upd_act_setup_with_action[195]-Failed connecting to 173.243.138.66:8890 upd_act_setup_with_action[191]-Trying FDS 209.222.136.7:8890 tcp_connect_fds[173]-Proxy tunneling enabled to 10.11.25.218:3128 negotiate_proxy_tunnel[116]-Error reading upd_comm_connect_fds[423]-Failed TCP connect upd_act_setup_with_action[195]-Failed connecting to 209.222.136.7:8890 do_setup[283]-Failed setup upd_cfg_get_host_by_name[95]-Failed to gethostbyname for update.fortiguard.net

Please help me, any advices to troubleshoot this problem?

Thanks