Hmm...

I do not want to insult your intelligence, but I don't know your exact experience using the tool; this can be difficult without physically having the tool to diagnose.

You cannot pull a Sequential Trip trigger and then actuate the trip lever like a "bump" fire, you must first actuate the trip lever, hold the tool to the work, and then pull the trigger. This must be done on every cycle.

The only other possible mechanical issue would be a worn or bent trip lever. If it is in effect too "short", it cannot actuate the levers under the trigger, and it will not reach the trigger valve stem to cycle the tool.

You may want to also contact a technical rep with Bostitch at this point, or call a rep at your local authorized Bostitch Service Center.
Find out where the closest ASC is to you by clicking on the below link:

www.bostitch.com/en-us/support/find-a-service-center

- MTR