VNP can't conncet successfully

Can you ping the endpoint?

I cat the logs out:
Oct 13 14:23:13 Chevy NetworkManager[739]: <info> Starting VPN service 'pptp'...
Oct 13 14:23:13 Chevy NetworkManager[739]: <info> VPN service 'pptp' started (org.freedesktop.NetworkManager.pptp), PID 26799
Oct 13 14:23:13 Chevy NetworkManager[739]: <info> VPN service 'pptp' appeared; activating connections
Oct 13 14:23:13 Chevy NetworkManager[739]: <info> VPN connection 'GO' (ConnectInteractive) reply received.
Oct 13 14:23:13 Chevy NetworkManager[739]: <info> VPN plugin state changed: starting (3)
Oct 13 14:23:14 Chevy NetworkManager[739]: ** Message: pppd started with pid 26803
Oct 13 14:23:14 Chevy NetworkManager[739]: <info> VPN connection 'GO' (Connect) reply received.
Oct 13 14:23:14 Chevy pppd[26803]: Plugin /usr/lib/pppd/2.4.6/nm-pptp-pppd-plugin.so loaded.
Oct 13 14:23:14 Chevy NetworkManager[739]: Plugin /usr/lib/pppd/2.4.6/nm-pptp-pppd-plugin.so loaded.
Oct 13 14:23:14 Chevy NetworkManager[739]: ** Message: nm-pptp-ppp-plugin: (plugin_init): initializing
Oct 13 14:23:14 Chevy pppd[26803]: pppd 2.4.6 started by root, uid 0
Oct 13 14:23:14 Chevy NetworkManager[739]: ** Message: nm-pptp-ppp-plugin: (nm_phasechange): status 3 / phase 'serial connection'
Oct 13 14:23:14 Chevy pppd[26803]: Using interface ppp0
Oct 13 14:23:14 Chevy pppd[26803]: Connect: ppp0 <--> /dev/pts/1
Oct 13 14:23:14 Chevy NetworkManager[739]: Using interface ppp0
Oct 13 14:23:14 Chevy NetworkManager[739]: Connect: ppp0 <--> /dev/pts/1
Oct 13 14:23:14 Chevy NetworkManager[739]: ** Message: nm-pptp-ppp-plugin: (nm_phasechange): status 5 / phase 'establish'
Oct 13 14:23:14 Chevy pptp[26807]: nm-pptp-service-26799 log[main:pptp.c:314]: The synchronous pptp option is NOT activated
Oct 13 14:23:14 Chevy NetworkManager[739]: nm_device_get_device_type: assertion 'NM_IS_DEVICE (self)' failed
Oct 13 14:23:14 Chevy NetworkManager[739]: <info> (ppp0): new Generic device (driver: 'unknown' ifindex: 13)
Oct 13 14:23:14 Chevy NetworkManager[739]: <info> (ppp0): exported as /org/freedesktop/NetworkManager/Devices/12
Oct 13 14:23:14 Chevy NetworkManager[739]: <info> devices added (path: /sys/devices/virtual/net/ppp0, iface: ppp0)
Oct 13 14:23:14 Chevy NetworkManager[739]: <info> device added (path: /sys/devices/virtual/net/ppp0, iface: ppp0): no ifupdown configuration found.
Oct 13 14:23:14 Chevy systemd[1]: Started ifup for ppp0.
Oct 13 14:23:14 Chevy systemd[1]: Starting ifup for ppp0...
Oct 13 14:23:14 Chevy sh[26815]: Unknown interface ppp0
Oct 13 14:23:14 Chevy pptp[26821]: nm-pptp-service-26799 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 1 'Start-Control-Connection-Request'
Oct 13 14:23:14 Chevy pptp[26821]: nm-pptp-service-26799 log[ctrlp_disp:pptp_ctrl.c:739]: Received Start Control Connection Reply
Oct 13 14:23:14 Chevy pptp[26821]: nm-pptp-service-26799 log[ctrlp_disp:pptp_ctrl.c:773]: Client connection established.
Oct 13 14:23:15 Chevy pptp[26821]: nm-pptp-service-26799 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 7 'Outgoing-Call-Request'
Oct 13 14:23:45 Chevy pppd[26803]: LCP: timeout sending Config-Requests
Oct 13 14:23:45 Chevy pppd[26803]: Connection terminated.
Oct 13 14:23:45 Chevy avahi-daemon[733]: Withdrawing workstation service for ppp0.
Oct 13 14:23:45 Chevy NetworkManager[739]: LCP: timeout sending Config-Requests
Oct 13 14:23:45 Chevy NetworkManager[739]: ** Message: nm-pptp-ppp-plugin: (nm_phasechange): status 11 / phase 'disconnect'
Oct 13 14:23:45 Chevy NetworkManager[739]: Connection terminated.
Oct 13 14:23:45 Chevy systemd[1]: Stopping ifup for ppp0...
Oct 13 14:23:45 Chevy ifdown[26974]: /sbin/ifdown: interface ppp0 not configured
Oct 13 14:23:45 Chevy systemd[1]: Stopped ifup for ppp0.
Oct 13 14:23:45 Chevy NetworkManager[739]: <info> devices removed (path: /sys/devices/virtual/net/ppp0, iface: ppp0)
Oct 13 14:23:45 Chevy NetworkManager[739]: <warn> VPN plugin failed: connect-failed (1)
Oct 13 14:23:45 Chevy NetworkManager[739]: ** Message: nm-pptp-ppp-plugin: (nm_phasechange): status 1 / phase 'dead'
Oct 13 14:23:45 Chevy pppd[26803]: Modem hangup
Oct 13 14:23:45 Chevy NetworkManager[739]: Modem hangup
Oct 13 14:23:45 Chevy NetworkManager[739]: <warn> VPN plugin failed: connect-failed (1)
Oct 13 14:23:50 Chevy NetworkManager[739]: ** Message: nm-pptp-ppp-plugin: (nm_exit_notify): cleaning up
Oct 13 14:23:50 Chevy pppd[26803]: Exit.
Oct 13 14:23:50 Chevy NetworkManager[739]: ** (nm-pptp-service:26799): WARNING **: pppd exited with error code 16
Oct 13 14:23:50 Chevy NetworkManager[739]: <warn> VPN plugin failed: connect-failed (1)
Oct 13 14:23:50 Chevy NetworkManager[739]: <info> VPN plugin state changed: stopped (6)
Oct 13 14:23:50 Chevy NetworkManager[739]: <info> VPN plugin state change reason: unknown (0)
Oct 13 14:23:50 Chevy NetworkManager[739]: <warn> error disconnecting VPN: Could not process the request because no VPN connection was active.
Oct 13 14:24:10 Chevy NetworkManager[739]: <info> VPN service 'pptp' disappeared
Oct 13 14:24:14 Chevy pptp[26821]: nm-pptp-service-26799 log[logecho:pptp_ctrl.c:677]: Echo Request received.
Oct 13 14:24:14 Chevy pptp[26821]: nm-pptp-service-26799 log[ctrlp_rep:pptp_ctrl.c:251]: Sent control packet type is 6 'Echo-Reply'

Yes, I tried ping the endpoint, it's OK.

Yes, I tried ping the endpoint, it's OK.

Please help me to see the logs, what happed and give me some suggest, thank you!

From the message:Oct 13 14:23:14 Chevy pptp[26807]: nm-pptp-service-26799 log[main:pptp.c:314]: The synchronous pptp option is NOT activated, I looks for the source code from pptp.c, which shows the synchronous failed, why？ But I can ping the endpoint at all.

/*** main *********************************************************************/
/* TODO: redesign to avoid longjmp/setjmp. Several variables here
   have a volatile qualifier to silence warnings from gcc < 3.0.
   Remove the volatile qualifiers if longjmp/setjmp are removed.
   */
int main(int argc, char **argv, char **envp)
{
    struct in_addr inetaddr;
    volatile int callmgr_sock = -1;
    char ttydev[PATH_MAX];
    char *tty_name;
    int pty_fd, tty_fd, gre_fd, rc;
    volatile pid_t parent_pid, child_pid;
    u_int16_t call_id, peer_call_id;
    char buf[128];
    int pppdargc;
    char **pppdargv;
    char phonenrbuf[65]; /* maximum length of field plus one for the trailing
                          * '\0' */
    char * volatile phonenr = NULL;
    volatile int launchpppd = 1, debug = 0;

    while(1){
        /* structure with all recognised options for pptp */
        static struct option long_options[] = {
            {"phone", 1, 0, 0},
            {"nolaunchpppd", 0, 0, 0},
            {"quirks", 1, 0, 0},
            {"debug", 0, 0, 0},
            {"sync", 0, 0, 0},
            {"timeout", 1, 0, 0},
            {"logstring", 1, 0, 0},
            {"localbind", 1, 0, 0},
            {"loglevel", 1, 0, 0},
     {"nobuffer", 0, 0, 0},
     {"idle-wait", 1, 0, 0},
     {"max-echo-wait", 1, 0, 0},
     {"version", 0, 0, 0},
     {"test-type", 1, 0, 0},
     {"test-rate", 1, 0, 0},
     {"rtmark", 1, 0, 0},
     {"nohostroute", 0, 0, 0},
            {0, 0, 0, 0}
        };
        int option_index = 0;
        int c;
        c = getopt_long (argc, argv, "", long_options, &option_index);
        if (c == -1) break; /* no more options */
        switch (c) {
            case 0:
                if (option_index == 0) { /* --phone specified */
                    /* copy it to a buffer, as the argv's will be overwritten
                     * by inststr() */
                    strncpy(phonenrbuf,optarg,sizeof(phonenrbuf));
                    phonenrbuf[sizeof(phonenrbuf) - 1] = '\0';
                    phonenr = phonenrbuf;
                } else if (option_index == 1) {/* --nolaunchpppd specified */
                    launchpppd = 0;
                } else if (option_index == 2) {/* --quirks specified */
                    if (set_quirk_index(find_quirk(optarg)))
                        usage(argv[0]);
                } else if (option_index == 3) {/* --debug */
                    debug = 1;
                } else if (option_index == 4) {/* --sync specified */
                    syncppp = 1;
                }

Is it possible for you to reboot the endpoint. It may help.

What the mean "endpoint" ? An VPN server? Router? or my system?

The system you are connecting to via the VPN.

via the VPN client, sorry

On the same computer, my windows system always link the VPN successfully, but the Ubuntu can't works fine, So I think it must be somewhere wrong with Ubuntu network packages. May I restore my network software packages as before?

This question was expired because it remained in the 'Open' state without activity for the last 15 days.