I have written a trigger an handler with test code which works perfectly in my full config sandbox. However when I go to deploy to production I get errors which say it can't insert an opportunity line item.  Why would this work in the sandbox but throw this error in production? Can anyone help me? I've spent 2 days changing my code trying to get this work and it makes not sense. It seems it can't create a product line item.  I've added line numbers where the trouble is.

Run Failures:
  lineItemTriggerHandlerTester.testAddDeleteLineItems System.DmlException: Insert failed. First exception on row 0; first error: CANNOT_INSERT_UPDATE_ACTIVATE_ENTITY, opportunityLineItemTrigger: execution of AfterInsert

caused by: System.NullPointerException: Attempt to de-reference a null object

Class.lineItemTriggerHandler.conItemSet: line 55, column 1
Class.lineItemTriggerHandler.onAfterInsert: line 29, column 1
Trigger.opportunityLineItemTrigger: line 6, column 1: []

Here is my class, trigger, and test code.

trigger opportunityLineItemTrigger on OpportunityLineItem (after insert,before delete) {

    lineItemTriggerHandler handler = new lineItemTriggerHandler();
    
    if(Trigger.isInsert){
6        handler.OnAfterInsert(Trigger.new);
    }
    else if(Trigger.isDelete){
        handler.OnDelete(Trigger.old, Trigger.oldMap);
    }
    
}

public with sharing class lineItemTriggerHandler {

    public void onAfterInsert(List<OpportunityLineItem> newRecords){
        Map<ID,OpportunityLineItem> newMap = new Map<ID,OpportunityLineItem>();
            
        for(OpportunityLineItem oli : newRecords){
                            
                newmap.put(oli.id,oli);            
        }
        
        //Create a list of all product line items attached to the opportunity
        List<OpportunityLineItem> lineItemChk = [SELECT 
        Id, 
        OpportunityId,
        Opportunity.StageName, 
        Quantity,
        Discount,
        ListPrice,
        TotalPrice,
        Product_Family__c,
        Billing_Rate__c,
        PricebookEntry.Product2.Family        
        FROM OpportunityLineItem WHERE Id IN : newmap.keyset()];
        
        
                
        if(lineItemChk.size() > 0){
             Integer cCount = productFamilySet(lineItemChk);
29             conItemSet(lineItemChk,cCount);                
        }
    }
    /* Sets Product_Family__c on the opportunity product line item */
    // Receives list of opportunitylineitems
    // Returns an integer    
    private Integer productFamilySet(List<OpportunityLineItem> items){
        integer cCount = 0;
        for(OpportunityLineItem oli: items){
            If(oli.Product_Family__c == null){
                oli.Product_Family__c = oli.PricebookEntry.Product2.Family;
            }
            If(oli.Product_Family__c == 'Consulting'){
                cCount = cCount + 1;    
            }
        }
        update items;
        return cCount;
    }
    
    /* Sets the PLIConsultingCalc on the opportunity to the number type 'Consulting' line items */
    // receives a list of oppline items and integer of number of consulting items
    
    private void conItemSet(List<OpportunityLineItem> items,Integer pCount){            
        Opportunity opp = [SELECT Id, PLIConsultingCalc__c FROM Opportunity Where Id =: items[0].OpportunityId];
        
        If(opp.PLIConsultingCalc__c == null){
        	opp.PLIConsultingCalc__c = 0;
        }
55        opp.PLIConsultingCalc__c = opp.PLIConsultingCalc__c + pCount;
        update opp;
        
    }
         
    
    public void OnDelete(List<OpportunityLineItem> toDeleteRecords, Map<ID,OpportunityLineItem> oldMap){
        
        integer dCount = 0;
        
        if(toDeleteRecords.size() > 0){
            for(OpportunityLineItem doli: toDeleteRecords){
                if(doli.Product_Family__c == 'Consulting'){
                    dCount = dCount - 1;
                }
            }
            if(dCount < 0){
                Opportunity dOpp = [SELECT Id, PLIConsultingCalc__c FROM Opportunity WHERE Id =: toDeleteRecords[0].OpportunityId];
                dOpp.PLIConsultingCalc__c = dOpp.PLIConsultingCalc__c + dCount;
                update dOpp;
            }            
        }
    }
}

@isTest(seeAllData=true)
private class lineItemTriggerHandlerTester{

     static testMethod void testAddDeleteLineItems() {
// set up our data for each test method
        /* Create Account */
        Account a = new Account(Name='test123', CurrencyIsoCode='USD',BillingCountry = 'United States');
        insert a;
                   
        /* Get the standard pricebook. There must be a standard pricebook already in the target org.  */        
        Pricebook2 standardPB = [SELECT Id,IsStandard FROM Pricebook2 WHERE IsStandard=true];     
        System.AssertEquals(true , standardPB.IsStandard == true);
        
        /* Create and check Opportunity */
        date futureDay = date.today();
        futureDay = futureDay.addDays(2);
        Opportunity opp = new Opportunity(name='testOppInProduction1234', stagename='2 - Validation',Z_ASP_monthly_Y__c=10,CurrencyIsoCode = 'USD',Pricebook2Id=standardPB.Id, Z_Top_Feeling__c=50, CloseDate=futureDay,LeadSource='Client Referral',Account=a);
        insert opp;
        Opportunity oppChk = [SELECT Name FROM Opportunity WHERE Id = :opp.Id];
        System.assertEquals(opp.Name,oppChk.Name);
        
        /* Setup Products */
        Product2 p1 = new Product2(Name='FF - Functional Consultant', Family='Consulting',IsActive=true);
        insert p1;
        Product2 p1Chk = [SELECT Name FROM Product2 WHERE Id = :p1.Id];
        System.assertEquals(p1Chk.Id,p1.Id);
        
        /* Setup PriceBook Entry */
        PricebookEntry pbe1 = new PricebookEntry(Pricebook2Id=standardPB.Id, Product2Id=p1.Id, CurrencyIsoCode = 'USD', UnitPrice=10, isActive=true);
        insert pbe1;
        PricebookEntry pbe1Chk = [SELECT Pricebook2Id FROM PricebookEntry WHERE ID = :pbe1.Id];
        System.assertEquals(pbe1.Id,pbe1Chk.Id); 
        
        /* Setup OpportunityLIneItem Check Product Family And PLIConsulting */
        OpportunityLineItem oli = new OpportunityLineItem(PriceBookEntryId=pbe1.Id, OpportunityId=opp.Id, Quantity=1, UnitPrice=10);
        insert oli;
        OpportunityLineItem oliChk = [SELECT PriceBookEntryId,Product_Family__c FROM OpportunityLineItem WHERE Id = :oli.Id];
        System.assertEquals(pbe1.Id, oliChk.PriceBookEntryId);
        System.assertEquals('Consulting',oliChk.Product_Family__c);
        
        /* Check PLIConsultingCalc field */
        Opportunity pliChk = [SELECT Id, PLIConsultingCalc__c FROM Opportunity WHERE Id = :opp.Id];
        System.assertEquals(1, pliChk.PLIConsultingCalc__c);
        
        /* Delete Line Item */
        delete oli;
        Opportunity delPLIChk = [SELECT Id, PLIConsultingCalc__c FROM Opportunity WHERE Id = :opp.Id];
        System.assertEquals(0,delPLIChk.PLIConsultingCalc__c);       
    }    
}

 Thanks for any help!!

Dahveed