Howdy Gang 
When working with an artifact registry trigger, it’s important to understand how triggers and pipelines are affected when collecting artifacts for the first time. In particular, there is a scenario that occurs when an artifact registry already contains multiple tags for a given image.
Suppose that the artifact registry has 10 tags for a given image, and a trigger is created. When the polling job from the delegate fetches all 10 tags and sends them across to the ng-manager, no trigger or pipeline is fired. This is because we wouldn’t want to run the pipeline for all the 10 tags that were pushed before the trigger creation. Doing so could result in leaving the system in an undesired state.
However, when an 11th tag or any subsequent tag is pushed, the trigger executes and runs the pipeline. This ensures that the system is in a desired state and any new changes are properly handled.
In summary, it’s important to understand that when collecting artifacts for the first time, triggering a pipeline for all previously collected tags could lead to undesired consequences. Instead, triggers and pipelines should be set up to handle subsequent changes and updates to the artifact registry. By following this approach, you can ensure that your system remains stable and functional over time.
Conclusion
When you experience the same, try pushing a new Tag to your GAR (Google Artifact Repository) this should cause the trigger to execute the pipeline as expected.