Jenkins Pipeline job isn't triggered on GitHub push
Solution mentioned by OP in a comment is correct.
Assuming you have a Github webhook for your Jenkins set up correctly and accessible (can be verified in the Github UI), you need to start the build manually once. Upon completion of the build, changes in the repository will automatically start new builds.
A note from user8888:
You actually need to manually start the build and the build must be successful. A failed build won't do anything.
With Github hook trigger for GITScm polling, you need to enable "Poll SCM" option because github push triggers git polling to verify if there is a new change and then runs the build if a change is found.You can keep the cron schedule empty.Github webhook with scm poll