error trying to use EF core code first

I am trying to use entity framework core code first, with an external sql server database hosted on AWS RDS. My aim is for EF to create my model database/tables automatically the first time I use Swagger to create an object. Currently, I am trying to enable migrations for my project before I allow EF code first to create the databases. Although when I try to Enable-Migrations I get an error: "The context type 'FitnessTrackerAPIContext' was not found in the assembly 'FitnessTrackerAPI'." As you can see from the below picture, the 'FitnessTrackerAPIContext' is in the 'FitnessTrackerAPI' so I am not sure why I am getting this error.

I am not quite sure if all my settings for EF core are correct s this is my first time using it.

Context:

namespace FitnessTrackerAPI.Data
{
    public class FitnessTrackerAPIContext : DbContext
    {
        public FitnessTrackerAPIContext (DbContextOptions<FitnessTrackerAPIContext> options)
            : base(options)
        {
        }

        public DbSet<FitnessTracker.UserData> Users { get; set; }

        public DbSet<FitnessTracker.WorkoutData> Workouts { get; set; }
    }
}

I have added the following to Startup.cs:

  services.AddDbContext<FitnessTrackerAPIContext>(options =>
            options.UseSqlServer(Configuration.GetConnectionString("FitnessTrackerAPIContext")));

My connection string in appsettings.json:

"ConnectionStrings": {"FitnessTrackerAPIContext": "Server=fitnessapi.clxnbxbuoxx1.eu-west-1.rds.amazonaws.com,1433;User ID=XXXXX;Password=XXXXX; Initial Catalog=fitnessapi; Database=fitnessapi; Connect Timeout=30;Encrypt=False;TrustServerCertificate=False;ApplicationIntent=ReadWrite;MultiSubnetFailover=False"

Do I need to add any other code? In program.cs or so? This is program.cs currently:

namespace FitnessTrackerAPI
{
    public class Program
    {
        public static void Main(string[] args)
        {
            CreateHostBuilder(args).Build().Run();
        }

        public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureWebHostDefaults(webBuilder =>
                {
                    webBuilder.UseStartup<Startup>();
                });
    }
}

Any advice would be appreciated.