ASP.NET core Web API Authorize Attribute return 404 Error & force redirect

maybe you have to add the AddAuthentication line after the AddControllers() line

Is it possible that DefaultChallengeScheme is redirecting to a page that does not exist such as a login page when it encounters the authorize attribute which could cause the 404?

Try setting the default challenge to the Jwt schema which returns not authorized.

services.AddAuthentication(options =>
{
    options.DefaultAuthenticateScheme = IdentityServerAuthenticationDefaults.AuthenticationScheme;
    options.DefaultChallengeScheme = JwtBearerDefaults.AuthenticationScheme;
})
.AddIdentityServerAuthentication(options =>
{
    options.Authority = "http://localhost:60415";
    options.ApiName = "mCareApi";
    options.RequireHttpsMetadata = false;
});

Or you could try the method I mentioned in the article below by providing a handler for the event.

services.AddAuthentication(IdentityServerAuthenticationDefaults.AuthenticationScheme)
.AddIdentityServerAuthentication(options =>
{
    options.JwtBearerEvents = new JwtBearerEvents
    {
        OnChallenge = context =>
        {
            context.Response.StatusCode = 401;
            return Task.CompletedTask;
        }
    };
    options.Authority = "http://localhost:60415";
    options.ApiName = "mCareApi";
    options.RequireHttpsMetadata = false;
});