IHttpContextAccessor in ActionFilterAttribute Identity.Name is Null

I have setup a AuthorizationFilter on Api controller action, during the first call the User Identity is being set but while accessing the httpContextAccessor in subsequent api requests the User.Identity.Name is null.

I have tried to use injection with setting up the HttpContextAccessor as singleton.

AuthorizationFilter code :

IIdentity identity = _singleSignOnUserService.GetUser(userInfo);
                        _httpContextAccessor.HttpContext.User = new GenericPrincipal(identity, null);

Startup.cs Injection code :

services.AddScoped<AuthAttribute>();
services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();

Controller code :

private readonly IHttpContextAccessor _httpContextAccessor;
TesController(IHttpContextAccessor httpContextAccessor)
{
   _httpContextAccessor = httpContextAccessor;
}

Why would _httpContextAccessor.HttpContext.User.Identity.Name be null even though the AuthorizeFilter has set the value?

I solved this by setting Authorization token in header of client requests to Webapi , it turned out the problem was because of the fact that client application - Angular and Core Webapi are hosted on different domains.