Hello developer heroes!

I'm working through the Apex modules on Trailhead and can't seem to get past this one: https://developer.salesforce.com/en/trailhead/force_com_programmatic_beginner/apex_triggers/apex_triggers_bulk.

Hopefully this doesn't read like a 'please complete the course for me' kinda post, but I have written a trigger that I believe meets the criteria but it isn't passing the check, so I wanted to seek the guidance of the experts.

The challenge is to do this:

Create an Apex trigger for Opportunity that adds a task to any opportunity set to 'Closed Won'.

To complete this challenge, you need to add a trigger for Opportunity. The trigger will add a task to any opportunity inserted or updated with the stage of 'Closed Won'. The task's subject must be 'Follow Up Test Task'.The Apex trigger must be called 'ClosedOpportunityTrigger'

- With 'ClosedOpportunityTrigger' active, if an opportunity is inserted or updated with a stage of 'Closed Won', it will have a task created with the subject 'Follow Up Test Task'.
- To associate the task with the opportunity, fill the 'WhatId' field with the opportunity ID.
- This challenge specifically tests 200 records in one operation.

And here is the trigger I have come up with, which compiles OK and stands up to a manual (though admittedly unbulkified) test:

trigger ClosedOpportunityTrigger on Opportunity (after insert, after update) {

    List<Task> taskList = new List<Task>();
    
    for (Opportunity opp : [SELECT Id, StageName FROM Opportunity WHERE StageName = 'Closed Won' AND Id IN :Trigger.new]){
                    
            taskList.add(new Task(Subject = 'Follow Up Test Task',
                                  WhatId = opp.Id));
       
    }

    if(taskList.size()>0){
        
        insert taskList;
        
    }
    
}

I have tried replacing the SOQL with a straightforward 'for (Opportunity opp : Trigger.new)' and having the taskList.add inside an IF that checks for Closed Won - no luck. I also thought about checking to see if the stage was being changed to Closed Won, rather than the trigger firing on every edit, but I don't think this is what the module is asking for.

Where do you think I'm going wrong?

Huge thanks in advance!

I'm trying to find information about how this app works in practice.

http://sites.force.com/appexchange/apex/listingDetail?listingId=a0N300000016ciJEAQ

 

We're on professional edition and the app information is unclear if it will work or not.  The App name implies that it won't work on professional edition, but the specs say otherwise.

 

I'm also a little skeptical that it's free.  It looks like a lot of development went into this product but why is it free and fully hosted on salesforce?  How does the publisher make money?