fix signalR configuration

Tsi1.Api/Tsi1.Api/Startup.cs

@@ -93,6 +93,8 @@ namespace Tsi1.Api
             services.AddScoped<IDataLoad, DataLoad>();
             services.AddScoped<ISurveyService, SurveyService>();
 
+            services.AddSingleton<PresenceTracker>();
+
             services.Configure<MailSettings>(Configuration.GetSection("MailSettings"));
             services.AddScoped<IEmailService, EmailService>();