systemctl status backuppc.service
Thats good. Does the web interface work? Try:
http://ip-of-server/backuppc/index.cgi?action="">
You might have to login. Check the file /etc/backuppc/htpasswd.
On my system it has the user and encrypted password for the
bcckuppc user. If you dont know the password then as root run
"passwd backuppc". That will allow you to change the backuppc
user password.