How to resolve errorCode: OAU-331

What is the returned error message associated with the error code? What API did you call?

I was calling the following:

ListAccountPhoneNumbersV2Parameters p = new ListAccountPhoneNumbersV2Parameters { perPage = 2000, usageType = new[] { "PhoneLine" } };

var resp = await restClient.Restapi().V2().Accounts().PhoneNumbers().Get(p);

And, got the following response:

StatusCode: 400, ReasonPhrase: 'Bad Request', Version: 1.1, Content: System.Net.Http.StreamContent, Headers:

{

  Connection: keep-alive

  CF-RAY: 9dbc0feeaf986d2e-SAT

  Vary: Accept-Encoding

  Vary: Origin

  Vary: Access-Control-Request-Method

  Vary: Access-Control-Request-Headers

  RCRequestId: 20f8a3a4-1ef1-11f1-9701-0050568d7162

  Pragma: no-cache

  AceRoutingKey: iad41-c01-ace01-69f65b5c44-wx92d_10.120.155.62

  RoutingKey: IAD41P14

  cf-cache-status: DYNAMIC

  Cache-Control: no-store

  Date: Fri, 13 Mar 2026 15:27:21 GMT

  Server: cloudflare

  Content-Length: 175

  Content-Language: en

  Content-Type: application/json

}

Content: {

  "error" : "invalid_request",

  "error_description" : "Unparseable assertion",

  "errors" : [ {

    "errorCode" : "OAU-331",

    "message" : "Unparseable assertion"

  } ]

}

Can you try this:

var resp = await restClient.Restapi().V2().Accounts(“~”).PhoneNumbers().Get(p);

BTW, the max perPage value in RingCentral API is normally 1000.