Hi @Jun Yan ,
Welcome to Microsoft Q&A forum and thanks for your query.
This can happen for various reasons like hitting concurrency limits, service outages, network failures and so on.
For possible resolution details, please refer to this doc and see if that helps: Pipeline status is queued or stuck for a long time
If it doesn't help, please do let us know what is Integration time being used on both source and Sink? If SHIR what is the version? Also please do share the queued pipeline runID so that we can double check with product team.
Let us know how it goes.
Thanks