Using groovy to set substitution variables for non admin users - REST API connection issue

Summary:

when we run below business rule, getting below error message, could you please check and update us.

"Details: A method called by the script failed on line: 40, with error: Error occurred: UNAUTHORIZED"


import groovy.json.JsonOutput
/*RTPS:1 {FCMthValue}*/
/*RTPS:2 {ActMthValue}*/

// Extracting RTP values
String varvalue1 = rtps.FCMthValue.enteredValue
String varvalue2 = rtps.ActMthValue.enteredValue

// Constructing URL for REST request
def Vaccines = operation.application.getConnection("Vaccines").getUrl() + "/HyperionPlanning/rest/v3/applications/Vaccines/plantypes/Input/substitutionvariables"

// Constructing JSON body for the REST request
def requestBody = JsonOutput.toJson([
items: [
[
"name": "FCMonthSpread",
"value": varvalue1,
"planType": "Input"
],
[
"name": "Actmonth",
"value": varvalue2 ,
"planType": "Input"
]
]
])

// Making POST request to update substitution variables