So I may be wrong on this, but it seems that you are registering your service incorrectly. According to the AddSingleton docs, you have set up the generic parameters backwards. It should be the type you want to add and then the implementation of that type.

For example, instead of: services.AddSingleton<ISingletonLoggerHelper, LoggerHelper>();, it should be: services.AddSingleton<LoggerHelper, ISingletonLoggerHelper>();. Hopefully this helps.