Cannot start vncserver: bind: Cannot assign requested address (99)

I use vnc over ssh with my Raspberry Pi. It has worked fine for a while, but after following these instructions to set up openvpn on my Raspberry Pi running Raspbian OS. I found that I can no longer access the VNC server on the Raspberry Pi. Forwarding x11 over ssh is working, but apparently, the vnc server cannot get access to its port, and so does not even start. $ sudo systemctl status vncserver-x11-serviced -l ● vncserver-x11-serviced.service - VNC Server in Service Mode daemon Loaded: loaded (/usr/lib/systemd/system/vncserver-x11-serviced.service; enabled) Active: active (running) since Sun 2018-01-21 14:25:11 GMT; 1s ago Main PID: 8896 (vncserver-x11-s) CGroup: /system.slice/vncserver-x11-serviced.service ├─8896 /usr/bin/vncserver-x11-serviced -fg ├─8898 /usr/bin/vncserver-x11-core -service └─8913 /usr/bin/vncagent service 14 Jan 21 14:25:11 raspberrypi vncserver-x11: TcpListenerManager: not accepting connections: failed to listen on at least one address. Jan 21 14:25:11 raspberrypi vncserver-x11: TcpListenerManager: not listening on [::1]::5900: bind: Cannot assign requested address (99) Jan 21 14:25:11 raspberrypi vncserver-x11: TcpListenerManager: not accepting connections: failed to listen on at least one address. Jan 21 14:25:11 raspberrypi vncserver-x11: TcpListenerManager: not listening on [::1]::5900: bind: Cannot assign requested address (99) Jan 21 14:25:11 raspberrypi vncserver-x11: TcpListenerManager: not accepting connections: failed to listen on at least one address. Jan 21 14:25:11 raspberrypi vncserver-x11: TcpListenerManager: not listening on [::1]::5900: bind: Cannot assign requested address (99) Jan 21 14:25:11 raspberrypi vncserver-x11: TcpListenerManager: not accepting connections: failed to listen on at least one address. Jan 21 14:25:11 raspberrypi vncserver-x11: TcpListenerManager: not listening on [::1]::5900: bind: Cannot assign requested address (99) Jan 21 14:25:11 raspberrypi vncserver-x11: TcpListenerManager: not accepting connections: failed to listen on at least one address. Jan 21 14:25:11 raspberrypi vncserver-x11: ConsoleDisplay: Found running X server (pid=1001) There doesn't appear to be anything running on that port. This is the output of lsof: $ sudo lsof -i tcp COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME cupsd 752 root 10u IPv4 13511 0t0 TCP localhost:ipp (LISTEN) cups-brow 756 root 5u IPv4 313573 0t0 TCP localhost:48450->localhost:ipp (CLOSE_WAIT) dnsmasq 914 dnsmasq 5u IPv4 11726 0t0 TCP *:domain (LISTEN) dnsmasq 914 dnsmasq 7u IPv6 11728 0t0 TCP *:domain (LISTEN) sshd 976 root 3u IPv4 11842 0t0 TCP *:2718 (LISTEN) tor 998 debian-tor 4u IPv4 12125 0t0 TCP 192.168.254.159:49042->ks3352401.kimsufi.com:8090 (ESTABLISHED) tor 998 debian-tor 7u IPv4 14489 0t0 TCP localhost:9050 (LISTEN) tor 998 debian-tor 11u IPv4 15915 0t0 TCP 172.94.70.220:47186->166.70.170.234:https (ESTABLISHED) sshd 5550 root 3u IPv4 315897 0t0 TCP 192.168.254.159:2718->192.168.254.47:64500 (ESTABLISHED) sshd 6322 morey 3u IPv4 315897 0t0 TCP 192.168.254.159:2718->192.168.254.47:64500 (ESTABLISHED) sshd 6322 morey 10u IPv4 319584 0t0 TCP localhost:6010 (LISTEN) Here's some other information that might be helpful: $ uname -a Linux raspberrypi 4.9.35-v7+ #1014 SMP Fri Jun 30 14:47:43 BST 2017 armv7l GNU/Linux $ vncserver --help VNC(R) Server 6.1.1 (r28093) ARMv6 (May 19 2017 12:59:35) It seems likely this has to do with either the changes to iptables or the disabling of ip6 in /etc/sysctl.conf, but I don't know how to troubleshoot it. Any ideas would be appreciated.