"Job for wg-quick@wg0.service failed because the control process exited with error code"

I am trying to install wireguard on Ubuntu 18.04 64 bit, following one of the video tutorials. Step systemctl start wg-quick@wg0.service finishes with Job for wg-quick@wg0.service failed because the control process exited with error code. See "systemctl status wg-quick@wg0.service" and "journalctl -xe" for details. Running systemctl status wg-quick@wg0.service gives: ● wg-quick@wg0.service - WireGuard via wg-quick(8) for wg0 Loaded: loaded (/lib/systemd/system/wg-quick@.service; indirect; vendor preset: enabled) Active: failed (Result: exit-code) since Sat 2023-03-11 00:02:48 UTC; 7min ago Docs: man:wg-quick(8) man:wg(8) https://www.wireguard.com/ https://www.wireguard.com/quickstart/ https://git.zx2c4.com/wireguard-tools/about/src/man/wg-quick.8 https://git.zx2c4.com/wireguard-tools/about/src/man/wg.8 Process: 18984 ExecStart=/usr/bin/wg-quick up wg0 (code=exited, status=1/FAILURE) Main PID: 18984 (code=exited, status=1/FAILURE) Mar 11 00:02:48 my-vps.name systemd: Starting WireGuard via wg-quick(8) for wg0... Mar 11 00:02:48 my-vps.name wg-quick: [#] ip link add wg0 type wireguard Mar 11 00:02:48 my-vps.name wg-quick: RTNETLINK answers: Operation not supported Mar 11 00:02:48 my-vps.name wg-quick: Unable to access interface: Protocol not supported Mar 11 00:02:48 my-vps.name wg-quick: [#] ip link delete dev wg0 Mar 11 00:02:48 my-vps.name wg-quick: Cannot find device "wg0" Mar 11 00:02:48 my-vps.name systemd: wg-quick@wg0.service: Main process exited, code=exited, status=1/FAILURE Mar 11 00:02:48 my-vps.name systemd: wg-quick@wg0.service: Failed with result 'exit-code'. Mar 11 00:02:48 my-vps.name systemd: Failed to start WireGuard via wg-quick(8) for wg0. Running journalctl -xe shows: Mar 10 23:46:27 my-vps.name wg-quick: [#] ip link add wg0 type wireguard Mar 10 23:46:27 my-vps.name wg-quick: RTNETLINK answers: Operation not supported Mar 10 23:46:27 my-vps.name wg-quick: Unable to access interface: Protocol not supported Mar 10 23:46:27 my-vps.name wg-quick: [#] ip link delete dev wg0 Mar 10 23:46:27 my-vps.name wg-quick: Cannot find device "wg0" My wg0.conf looks like: [Interface] PrivateKey = myprivatekeyhere Address = 10.0.0.1/24 ListenPort = 51830 PostUp = iptables -A FORWARD -i %i -j ACCEPT; iptables -t nat -A POSTROUTING -o venet0 -j MASQUERADE PostDown = iptables -D FORWARD -i %i -j ACCEPT; iptables -t nat -D POSTROUTING -o venet0 -j MASQUERADE modprobe wireguard says: modprobe: FATAL: Module wireguard not found in directory /lib/modules/4.15.0 ls /lib/modules returns: 4.15.0 4.15.0-206-generic uname -r shows: 4.15.0 Rebooting did not help. Searching did not help.