You run a "sudo ps -ef | grep sonar" and find Sonar to be running. You run "sudo sytemctl status sonar" and find that it is active. You run nmap or netstat and see port activity from the sonar service. Sonar is listening. When you go to a web browser over the right port (e.g., http://x.x.x.x:9000/) you do not see any web page. There is no evidence you can connect. How do you log into SonarQube via a web browser?
Use "/sonar" in the URL. Rather than a program like Jenkins, the URL may need to be constructed with a "/sonar" appended to it like this:
# Where x.x.x.x is the external IP address of the server. You can find it by running this command from the back-end: ip addr show | grep inet
You will ignore the 127.0.0.1 from the results. You can change the base URL in sonar.properties. If you want to do this, see this posting.