C# dotAPNS push notification stops work on server and need to restart server to make it working

I tried this code to sent push notification in iOS and it's working but only for some duration and then it is not responding from var response = apns.SendAsync(push).Result; and if I need to sent push notification again then I need to restart the server and then it is start working again but only for some duration.

I am using dotAPNS v4.0.30319 NuGet package to sent push notification. I am using amazonaws server.

Here, I am adding a code sample for a bit more clarity.

 public bool SendIOSNotification(Dictionary<string, Dictionary<string, string>> iosDictionary, ILog log = null)
    {
        
        string p8File= HttpContext.Current.Server.MapPath("*******");
        var options = new ApnsJwtOptions()
        {
            BundleId = "*****",
            CertFilePath = p8File, // use either CertContent or CertFilePath, not both
            KeyId = "******",
            TeamId = "*****"
        };
        var apns = ApnsClient.CreateUsingJwt(new HttpClient(new WinHttpHandler()), options);

        var push = new ApplePush(ApplePushType.Alert)
            .AddBadge(1)
            .AddSound("sound.caf");
            foreach (var itemKey in iosDictionary)
        {
            _log.DebugFormat("========== IOS ==========");
            _log.DebugFormat("Device Item {0}", itemKey);
            string payLoadCatgory = string.Empty;

            push.AddCustomProperty("content-available", "1", true)
            
                .AddToken(itemKey.Key.ToString());                              

            foreach (var itemValue in itemKey.Value)
            {
                try
                {
                    if (!itemValue.Key.ToLower().Contains("id"))
                    {
                        push.AddCustomProperty(itemValue.Key, itemValue.Value, true);
                    }
                    else
                    {
                        push.AddCustomProperty(itemValue.Key, Convert.ToInt64(itemValue.Value), true);
                    }

                    if (itemValue.Key.ToLower().Contains("category"))
                    {
                        payLoadCatgory = itemValue.Value;
                    }
                }
                catch (Exception ex)
                {
                    log.Error(string.Format("Error in send Notification to IOS :: DeviceToken is {0}", itemKey.Key));
                }
            }
            try
            {
                _log.Debug("Start send notification");
                var response =  apns.SendAsync(push).Result;
                _log.Debug("Sent notification");
                if (response.IsSuccessful)
                {
                    log.Info(string.Format("An alert push has been successfully sent!"));
                    return true;
                }
                else
                {
                    switch (response.Reason)
                    {
                        case ApnsResponseReason.BadCertificateEnvironment:
                           break;
                     
                        default:
                            throw new ArgumentOutOfRangeException(nameof(response.Reason), response.Reason, null);
                    }
                    log.Error(string.Format("Failed to send a push, APNs reported an error: " + response.ReasonString));
                }
            }
            catch (TaskCanceledException)
            {
                log.Error(string.Format("Failed to send a push: HTTP request timed out."));
            }
            catch (HttpRequestException ex)
            {
                log.Error(string.Format("Failed to send a push. HTTP request failed: " + ex));
            }
            catch (Exception ex)
            {
                log.Error(string.Format("Failed to send a push. HTTP request failed: " + ex));
                return false;
            }
        }
        return false;
    }