No authentication handler is configured to handle the scheme: Identity.Application

I receive the above error after I have successfully registered a user and confirmed authentication. The error occurs when I try to call

await _signInManager.SignInAsync(applicationUser, isPersistent);

I first assign the service to the IServiceCollection with this:

services.AddIdentity<ApplicationUser, IdentityRole<int>>(
            config => { config.User.RequireUniqueEmail = true;
                config.Cookies.ApplicationCookie.LoginPath = "/Account/Login";
                config.Cookies.ApplicationCookie.Events = new CookieAuthenticationEvents()
                {
                    OnRedirectToLogin = async ctx =>
                    {
                        if (ctx.Request.Path.StartsWithSegments("/api") && ctx.Response.StatusCode == 200)
                        {
                            ctx.Response.StatusCode = 401;
                        }
                        else
                        {
                            ctx.Response.Redirect(ctx.RedirectUri);
                        }
                        await Task.Yield();
                    }
                };
            }).AddEntityFrameworkStores<VisualJobsDbContext, int>()
          .AddDefaultTokenProviders();

and in my Config method of startup I call 

app.UseIdentity();

if I change my call to be:

var myVal = await _signInManager.PasswordSignInAsync(applicationUser, password, true, false);

them myVal gives back 'Failed' when it should have succeeded. An error doesn't get thrown either, so I suspect it's failing silently in the background for the same reason as the first type of call and just returning 'Failed'