Store does not implement IUserRoleStore ASP.NET Core Identity
In Startup.cs, I was missing AddRoles so services.AddDefaultIdentity<PortalUser>() .AddEntityFrameworkStores<ApplicationDbContext>(); should be services.AddDefaultIdentity<PortalUser>() .AddRoles<IdentityRole>() .AddEntityFrameworkStores<ApplicationDbContext>(); Note: The order is critical. AddRoles must come before AddEntityFrameworkStores