Challenge Not yet complete... here's what's wrong: 
The runWarehouseEquipmentSync method does not appear to have run successfully. Could not find a successfully completed @future job for this method. Make sure that you run this method at least one before attempting this challenge. Since this method is annotated with the @future method, you may want to wait for a few seconds to ensure that it has processed successfully.

here is my code

public with sharing class WarehouseCalloutService {
    
    private static final String WAREHOUSE_URL = 'https://th-superbadge-apex.herokuapp.com/equipment';
    @future(callout=true)
    // complete this method to make the callout (using @future) to the
    // REST endpoint and update equipment on hand.
    public static void runWarehouseEquipmentSync(){
        Http http = new Http();
        HttpRequest request = new HttpRequest();
        request.setEndpoint(WAREHOUSE_URL);
        request.setMethod('GET');
        HttpResponse response = http.send(request);
        // If the request is successful, parse the JSON response.
        String ret = '';
        if (response.getStatusCode() == 200) {
            // Deserialize the JSON string into collections of primitive data types.
            List<Object> results = (List<Object>) JSON.deserializeUntyped(response.getBody());
            
            List<Product2> LstProduct = new List<Product2>();
            for(Object obj : results)
            { 
                Map<String, Object> mapobj = (Map<String, Object>)obj;
                Product2 product = new Product2();
                           
                Integer maintenanceperiod = (Integer)mapobj.get('maintenanceperiod');               
                Integer Lifespan = (Integer)mapobj.get('lifespan');
                Integer Cost = (Integer)mapobj.get('cost');
                Boolean replacement = (Boolean)mapobj.get('replacement');
                Integer quantity = ((Integer)mapobj.get('qIntegerntity'));
                product.Name  = (String)mapobj.get('name'); 
                product.Maintenance_Cycle__c = Integer.valueof(maintenanceperiod);
                product.Cost__c = Cost;
                product.Current_Inventory__c = quantity;
                product.Lifespan_Months__c = Lifespan; 
                product.Replacement_Part__c = replacement;
                product.Warehouse_SKU__c = (String) mapobj.get('sku');
                product.ProductCode = (String)mapobj.get('_id');       
                LstProduct.add(product);
            }
            
            System.debug(LstProduct);
             upsert LstProduct Warehouse_SKU__c;
        
        }
        
       
    }
}

For the above qus I wrote the below code : 

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

List<Task> t1=new List<Task>();


for (opportunity a :[select ID,StageName  from opportunity where StageName='Closed Won' and ID IN :Trigger.New])
{


t1.add(new Task(subject= 'Follow Up Test Task', WhatId=a.ID));

if(t1.size() >0 && t1.size()<=200)
{
insert t1;
}
}
}


But getting a error like   :
Challenge Not yet complete... here's what's wrong: 
There was an unexpected error in your org which is preventing this assessment check from completing: System.DmlException: Insert failed. First exception on row 0; first error: CANNOT_INSERT_UPDATE_ACTIVATE_ENTITY, trig_conts_opprty: execution of AfterInsert caused by: System.DmlException: Insert failed. First exception on row 0 with id 0032800000QkI6aAAF; first error: INVALID_FIELD_FOR_INSERT_UPDATE, cannot specify Id in an insert call: [Id] Trigger.trig_conts_opprty: line 10, column 1: []


Anyone please tell me the possible reason for the error ?