How to retrieve Id from the response which suddenly fails - groovy

Question

We are using MS Graph api to collect Ad user information. One of our method suddenly stop working when using our groovy script.
Actually when calling the Graph API url from POSTMAN directly for requesting user information we receive the following response
{
"#odata.context": "https://graph.microsoft.com/v1.0/$metadata#users",
"value": [
{
"businessPhones": [],
"displayName": "Rhea Sam",
"givenName": null,
"jobTitle": null,
"mail": "user#mydoamin.com",
"mobilePhone": null,
"officeLocation": null,
"preferredLanguage": null,
"surname": null,
"userPrincipalName": "user#mydoamin.com#EXT##rlxcom.onmicrosoft.com",
"id": "05906321-ed38-4bfd-9c9e-02bfb7d32405"
}
]
}
Until now our groovy script call for that same API was working well but then suddenly stop working
Here is calling method code we are using
public String getGuestUserId(String AuthToken,String userEmail){
String _userId
def http = new HTTPBuilder("https://graph.microsoft.com/v1.0/users/?")
http.request(GET) {
requestContentType = ContentType.JSON
//uri.query = [ $filter:"mail eq '$userEmail'"].toString()
uri.query=[$filter:"mail eq '$userEmail'"]
headers.'Authorization' = "Bearer " + AuthToken
response.success = { resp, json ->
if (**json.value**){
_userId=**json.value**[0].id
}
else
_userId=-1 // user does not exist
}
// user ID not found : error 404
response.'404' = { resp ->
_userId = 'Not Found'
}
}
_userId
}
What is happening when executing this method now is that the json.value return an error saying :
"No such property: value for class: java.lang.Object"
Note that if we try to return just the json.toString() then it return only
"#odata.context": "https://graph.microsoft.com/v1.0/$metadata#users",
"value": []
What is wrong and how to solve it as it is suppose to return same information as the POSTMAN response in which we are concerned only to retrive the Id of teh user from the response
Thanks for your help
regards