Calling a Oracle REST API in groovy script under Object triggers

receiving null response while calling oracle standard rest API in groovy ,

please help with this, we are trying to call groovy based on certain conditions to update interface date on subscription bill lines

1. webservice registered under application composer

I tried with Patch and Put, called this rest API in post man and it works

2. under standard objects > subscription > service scripts > object triggers

update interface date on Subscription.

def SubscriptionNumber_v = SubscriptionNumber;
def sub_products = products;
 
   while(sub_products.hasNext()){
           def sub_productsRow = sub_products.next();       
           def SubscriptionProductPuid_v = sub_productsRow.SubscriptionProductPuid;
           def sub_billLines = sub_productsRow.billLines;
    
          while(sub_billLines.hasNext()){
                  def sub_billLinesRow = sub_billLines.next();