Groovy script to notify agent when request is updated

Summary:

Content (please ensure you mask any confidential information):

My groovy script is supposed to send a bell/email notification to agents when their request is updated but its not pushing anything through. Can you let me know if there is an issue with my script? I also set the trigger to 'AfterTrasactionPosted;

if (isAttributeChanged('LastUpdatedBy') && (LastUpdatedBy == PrimaryContactPartyId)) {
try {
def map = new HashMap();

    // Create notification message

    def messageText = 'The Primary Contact has updated Service Request (SR' + SrNumber + ' - ' + Title + '). Please review the changes.';


    // Identify the recipient (Agent assigned to the request)

    def recipientPartyId = AssigneeResourceId;


    // Specify notification channels