As part of the latest Release 20.3.1 - Build 9228, triggers integration authentication originally based on oAUTH authentication setup to access pipeline, has now been changed and moved to Adobe I/O.
Learn more here to understand how to configure Adobe I/O for Adobe Experience Cloud triggers: Configuring Adobe I/O for Adobe Experience Cloud Triggers
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In case you have any ideas and/or suggestions regarding the Campaign Classic product, then kindly submit them here.
Sukrity Wadhwa