Plugin Error on Update

Hi All,

I am brand new to CRM and CRM Plugins.  I created a c# plugin and registered it on a Create Step.  The plugin works great.  When I create a record of type A it should create related records of type B.  This works great.

Now I want to change the step to create the related B records when A is updated instead of created.  I unregistered the step and reregistered the step as an Update message.  When I save a recod of type A I get the following error message:

Unexpected exception from plug-in (Execute): PlugIn_ATF_Application_Requirements.PluginATFApplicationRequirements: System.Collections.Generic.KeyNotFoundException: The given key was not present in the dictionary. If you contact support, please provide the technical details.

My Plugin Code is below and the registration step is below that.  Any help would be appreciated!

using Microsoft.Xrm.Sdk;
using Microsoft.Xrm.Sdk.Query;

using System;
using System.ServiceModel;


namespace PlugIn_ATF_Application_Requirements
{
    public class PluginATFApplicationRequirements : IPlugin
    {
        void IPlugin.Execute( IServiceProvider serviceProvider )
        {
            // Obtain the tracing service
            ITracingService tracingService =
            ( ITracingService )serviceProvider.GetService( typeof( ITracingService ) );

            // Obtain the execution context from the service provider.  
            IPluginExecutionContext context = ( IPluginExecutionContext )serviceProvider.GetService( typeof( IPluginExecutionContext ) );

            // The InputParameters collection contains all the data passed in the message request.  
            if ( context.InputParameters.Contains( "Target" ) && context.InputParameters["Target"] is Entity )
            {
                // Obtain the target entity from the input parameters.  
                Entity entity = ( Entity )context.InputParameters["Target"];

                tracingService.Trace( $"Passed in Entity Information. LogicalName: {entity.LogicalName} aws_name: {entity.Attributes["aws_name"]} applicationID: {entity.Id} applicationTypeID: {entity.Attributes["aws_accreditationapplicationtypeid"]}" );
                // Obtain the organization service reference which you will need for web service calls.  
                IOrganizationServiceFactory serviceFactory = ( IOrganizationServiceFactory )serviceProvider.GetService( typeof( IOrganizationServiceFactory ) );
                IOrganizationService service = serviceFactory.CreateOrganizationService( context.UserId );

                try
                {
                    // Plug-in business logic goes here.
                    //  Findout what object brought us here
                    Guid accreditationApplicationID = entity.Id;
                    // Fetch an ATF Appliction record based on the passed in ID and all requirements for the applicationTypeID found on the Application
                    Entity atfApplication = service.Retrieve( "aws_accreditationapplication", accreditationApplicationID, new ColumnSet( true ) );
                    tracingService.Trace( $"Found application: {atfApplication.Attributes["aws_name"]}" );

                    //  2021-09-17  Steven Rieger
                    //  Added check to see if requirements exist already.  If so, we are done here.  If not, then create them.

                    //  Look for existing requirements for this applicatio
                    var queryExpression = new QueryExpression()
                    {
                        EntityName = "aws_accreditationapplicationrequirement",
                        //  Fetch all columns
                        ColumnSet = new ColumnSet( true ),
                        Criteria = new FilterExpression()
                        {
                            //  Pull the applicationTypeID from the application record
                            Conditions =
                            {
                                new ConditionExpression( "aws_accreditationapplicationid", ConditionOperator.Equal, accreditationApplicationID )
                            }
                        }
                    };
                    //  Do the fetch
                    EntityCollection receivedRequirements = service.RetrieveMultiple( queryExpression );
                    if ( receivedRequirements.Entities.Count == 0 )
                    {
                        tracingService.Trace( "No Requirements Found.  Let's create them!" );
                        //  Fetch the requirements setup for the Application Type ID
                        queryExpression = new QueryExpression()
                        {
                            EntityName = "aws_accreditationrequirement",
                            //  Fetch all columns
                            ColumnSet = new ColumnSet( true ),
                            Criteria = new FilterExpression()
                            {
                                //  Pull the applicationTypeID from the application record
                                Conditions = { new ConditionExpression( "aws_accreditationapplicationtypeid", ConditionOperator.Equal, ( ( EntityReference )atfApplication["aws_accreditationapplicationtypeid"] ).Id ) }
                            }
                        };

                        //  Do the fetch
                        receivedRequirements = service.RetrieveMultiple( queryExpression );  //"aws_accreditationrequirement", retrievedAccreditationApplication.aws_AccreditationApplicationTypeId.Id, requireMentColumns );

                        //  Loop through all the requirements found and add them to the ATF Application
                        tracingService.Trace( "Retrieved {0} requirements\n", receivedRequirements.Entities.Count );
                        foreach ( Entity requirement in receivedRequirements.Entities )
                        {
                            tracingService.Trace( $"Processing Requirement {requirement["aws_name"]}\n" );
                            Guid applicationRequirementID = new Guid();

                            //  Create the new app requirement Entity
                            Entity applicationRequirement = new Entity( "aws_accreditationapplicationrequirement" );
                            //  Populate the requird fields...
                            applicationRequirement.Attributes.Add( "aws_accreditationapplicationid", new EntityReference( atfApplication.LogicalName, atfApplication.Id ) );
                            applicationRequirement.Attributes.Add( "aws_accreditationrequirementid", new EntityReference( requirement.LogicalName, requirement.Id ) );
                            applicationRequirement.Attributes.Add( "statuscode", 1 );
                            applicationRequirement.Attributes.Add( "aws_name", requirement.Attributes["aws_name"] );

                            applicationRequirementID = service.Create( applicationRequirement );
                            tracingService.Trace( $"Created Requirement: {requirement["aws_name"]}\n" );
                        }
                    }
                }

                catch ( FaultException<OrganizationServiceFault> ex )
                {
                    tracingService.Trace( "PluginATFApplicationRequirements: {0}", ex.ToString() );
                    throw new InvalidPluginExecutionException( "An error occurred in PluginATFApplicationRequirements.", ex );
                }

                catch ( Exception ex )
                {
                    tracingService.Trace( "PluginATFApplicationRequirements: {0}", ex.ToString() );
                    throw;
                }
            }
        }
    }
}

community.dynamics.com/.../2021_2D00_09_2D00_17_5F00_9_2D00_00_2D00_10.pdf

I'm using on prem version 9.x of CRM