[Jenkins Lab - Install] i can't start Jenkins.service

I tried to follow the instructions in the Managing systemd services but could not start jenkins.service. I changed the port to 8081 to not duplicate the already used port of 8080. However, I still could not start jenkins.service. , I execute the next command directly as shown in the picture, then jenkins works, helping me process

Which lab is this? I don’t think you install Jenkins on the jump_host.