Symptom
One or more GitLab runners are configured, show as green in the runners list but CI jobs are not being picked up.
Possible cause and fix
By default GitLab runners will only run jobs tagged with a tag which matches their configuration. To allow a runner to run untagged builds: navigate to the list of runners, click the "pencil icon" next to the runner and ensure that the "Run untagged jobs" option is selected.