Hi @Arthur Choi ,
Welcome to Microsoft Q&A forum and thanks for using Azure Services.
As I understand from the question, error is coming 'Type=System.Threading.Tasks.TaskCanceledException,Message=A task was canceled.,Source=mscorlib,' when a Pipeline is executed by Trigger.
The Task got cancelled which signifies probably a Timeout has occurred in the activities used in the Pipeline.
Please check if the pipeline has dependency on other pipelines and those executed fine.
You may also check the trigger state if it is active.
Additionally, if the above checks do not help, please share the snippet of the pipeline and configuration details to investigate further.