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From what you describe, the trigger seems to be correct.
You can try a "has opportunity" filter with the same criteria (deal type, team and total closed seats and stage is closed won) to check that you have leads in the DB with this type of opened oppy. if the smart list comes up empty, then it would explain why the trigger did not fire. the most likely reason is that the contacts are not really attached to the oppy, in the "Opportunity contact role" section.