Error posting to web api on Azure using zumo on unity - azure

Question

We have an error using some plugin on unity.
It worked for a few years, suddenly at 1.6.18 stopped working.
We are using webapi through azure app service.
The error is:
{System.Net.WebException: Error getting response stream (Write: BeginWrite failure): SendFailure ---> System.IO.IOException: BeginWrite failure
at System.Net.Sockets.NetworkStream.BeginWrite (System.Byte[] buffer, Int32 offset, Int32 size, System.AsyncCallback callback, System.Object state) [0x00000] in <filename unknown>:0
at Mono.Security.Protocol.Tls.RecordProtocol.BeginSendRecord (ContentType contentType, System.Byte[] recordData, System.AsyncCallback callback, System.Object state) [0x00000] in <filename unknown>:0
at Mono.Security.Protocol.Tls.RecordProtocol.SendRecord (ContentType contentType, System.Byte[] recordData) [0x00000] in <filename unknown>:0
at Mono.Security.Protocol.Tls.RecordProtocol.SendAlert (Mono.Security.Protocol.Tls.Alert alert) [0x00000] in <filename unknown>:0
at Mono.Security.Protocol.Tls.RecordProtocol.SendAlert (AlertDescription description) [0x00000] in <filename unknown>:0
at Mono.Security.Protocol.Tls.SslStreamBase.AsyncHandshakeCallback (IAsyncResult asyncResult) [0x00000] in <filename unknown>:0
--- End of inner exception stack trace ---
Authorization Error: 0
UnityEngine.Debug:Log(Object)
Assets.Scripts.Services.LoginService:EmailAuthenticationCallback(IRestResponse`1) (at Assets/Scripts/Services/LoginService.cs:41)
Unity3dAzure.MobileServices.<Invoke>c__AnonStorey0`1:<>m__0(IRestResponse) (at Assets/MobileServices-master/client/MobileServiceClient.cs:104)
RestSharp.<ExecuteAsync>c__AnonStorey0:<>m__0(IRestResponse, RestRequestAsyncHandle) (at Assets/Source/RestClientExtensions.cs:18)
RestSharp.RestClient:ProcessResponse(IRestRequest, HttpResponse, RestRequestAsyncHandle, Action`2) (at Assets/Source/RestClient.Async.cs:110)
RestSharp.<ExecuteAsync>c__AnonStorey0:<>m__0(HttpResponse) (at Assets/Source/RestClient.Async.cs:83)
RestSharp.Http:ExecuteCallback(HttpResponse, Action`1) (at Assets/Source/Http.Async.cs:328)
RestSharp.Http:RequestStreamCallback(IAsyncResult, Action`1) (at Assets/Source/Http.Async.cs:224)
RestSharp.<WriteRequestBodyAsync>c__AnonStorey1:<>m__0(IAsyncResult) (at Assets/Source/Http.Async.cs:153)
System.Net.WebConnection:InitConnection(Object)
Debug.Log("Status: " + restResponse.StatusCode + " Uri:" + restResponse.ResponseUri);
if (restResponse.Data != null && restResponse.Data.User != null && restResponse.Data.IsValid)
{
new CurrentAccount().Set(restResponse.Data);
}
if (restResponse.StatusCode == HttpStatusCode.OK)
{
_callback.Invoke(restResponse.Data);
}
else
{
Debug.Log("Authorization Error: " + restResponse.StatusCode);
_callback.Invoke(new LoginResponseDto());
}
}
}
}