Question
Why isn't my trigger running when I mass update tickets?
Answer
When you update tickets in bulk, the event is recorded as a Web Service (API) update.
If your trigger has the condition Update via | is not | Web Service (API), your updates will not activate the trigger, because the update_via attribute in your ticket events is recorded as an API call.
To make sure your triggers run correctly, remove this Update via | is not | Web Service (API) condition. If that condition is necessary, consider creating a separate trigger specifically for bulk updates.
For more information, see these articles: