tcp :53: bind: address already in use

Trying to install NextDNS (via the one line command-rookie user) on Ubuntu Server 20.04.1, clean install, all answers with Y and yet I receive the following errors.

Scope would be to serve DNS requests with split WireguardVPN.

when:

 nextdns activate

Error: setup resolv.conf: write /etc/resolv.conf.nextdns-tmp: open /etc/resolv.conf.nextdns-tmp: permission denied

nextdns start results in

Error: systemctl start nextdns.service: exit status 1: Failed to start nextdns.service: Interactive authentication required.
See system logs and 'systemctl status nextdns.service' for details.

nextdns log

Jan 03 11:40:38 cc1-dns systemd[1]: Started NextDNS DNS53 to DoH proxy..
Jan 03 11:40:38 cc1-dns nextdns[20810]: Starting NextDNS 1.9.4/linux on localhost:53
Jan 03 11:40:38 cc1-dns nextdns[20810]: Listening on TCP/127.0.0.1:53
Jan 03 11:40:38 cc1-dns nextdns[20810]: Listening on UDP/127.0.0.1:53
Jan 03 11:41:15 cc1-dns nextdns[20810]: Received signal: terminated
Jan 03 11:41:15 cc1-dns systemd[1]: Stopping NextDNS DNS53 to DoH proxy....
Jan 03 11:41:15 cc1-dns nextdns[20810]: Stopping NextDNS 1.9.4/linux
Jan 03 11:41:15 cc1-dns nextdns[20810]: NextDNS 1.9.4/linux stopped
Jan 03 11:41:15 cc1-dns systemd[1]: nextdns.service: Succeeded.
Jan 03 11:41:15 cc1-dns systemd[1]: Stopped NextDNS DNS53 to DoH proxy..
Jan 03 11:41:16 cc1-dns systemd[1]: Started NextDNS DNS53 to DoH proxy..
Jan 03 11:41:16 cc1-dns nextdns[21067]: Starting NextDNS 1.9.4/linux on :53
Jan 03 11:41:16 cc1-dns nextdns[21067]: Listening on TCP/:53
Jan 03 11:41:16 cc1-dns nextdns[21067]: Starting mDNS discovery
Jan 03 11:41:16 cc1-dns nextdns[21067]: Listening on UDP/:53
Jan 03 11:41:16 cc1-dns nextdns[21067]: Startup failed: proxy: tcp: listen tcp :53: bind: address already in use
Jan 03 11:41:16 cc1-dns nextdns[21067]: Error: proxy: tcp: listen tcp :53: bind: address already in use
Jan 03 11:41:16 cc1-dns systemd[1]: nextdns.service: Main process exited, code=exited, status=1/FAILURE
Jan 03 11:41:16 cc1-dns systemd[1]: nextdns.service: Failed with result 'exit-code'.
Jan 03 11:42:04 cc1-dns systemd[1]: Started NextDNS DNS53 to DoH proxy..
Jan 03 11:42:04 cc1-dns nextdns[21128]: Starting NextDNS 1.9.4/linux on :53
Jan 03 11:42:04 cc1-dns nextdns[21128]: Error: proxy: tcp: listen tcp :53: bind: address already in use
Jan 03 11:42:04 cc1-dns nextdns[21128]: Listening on TCP/:53
Jan 03 11:42:04 cc1-dns nextdns[21128]: Starting mDNS discovery
Jan 03 11:42:04 cc1-dns nextdns[21128]: Listening on UDP/:53
Jan 03 11:42:04 cc1-dns nextdns[21128]: Startup failed: proxy: tcp: listen tcp :53: bind: address already in use
Jan 03 11:42:04 cc1-dns systemd[1]: nextdns.service: Main process exited, code=exited, status=1/FAILURE
Jan 03 11:42:04 cc1-dns systemd[1]: nextdns.service: Failed with result 'exit-code'.