Error de conexión en UserManager CreateAsync

Recibo el siguiente error al intentar crear un nuevo usuario utilizando el método UserManager CreateAsync. Estoy usando un IdentityUser e IdentityRole sin modificar. Tengo algunos DBSets que se rellenan con datos de la base de datos, por lo que la lectura no es un problema, solo escribirlo parece ser.

    {System.InvalidOperationException: Connection must be valid and open to commit transaction at MySql.Data.MySqlClient.MySqlTransaction.Commit()
   at Microsoft.EntityFrameworkCore.Storage.RelationalTransaction.Commit()
   at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.<ExecuteAsync>d__10.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.<SaveChangesAsync>d__54.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.<SaveChangesAsync>d__52.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.EntityFrameworkCore.DbContext.<SaveChangesAsync>d__35.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Identity.EntityFrameworkCore.UserStore`9.<CreateAsync>d__36.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Identity.UserManager`1.<CreateAsync>d__68.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Identity.UserManager`1.<CreateAsync>d__73.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at Controllers.Auth.AuthController.<Register>d__9.MoveNext() in AuthController.cs:line 102}

Estoy usando;

• MySQL Entity Framework Core 7.0.7-m61
• Visual Studio 2017
• ASP.NET Core MVC 1.1.0
• Identidad 1.1

La línea 102 mencionada en el error es var resultado = espera userManager.CreateAsync (newUser, model.Password);

        [HttpPost]
        public async Task<ActionResult>Register(RegisterViewModel model)
        {
            try
            {
                if (ModelState.IsValid)
                {
                    var newUser = new IdentityUser
                    {
                        Email = model.Email,
                        UserName = model.Username
                    };

                    var result = await _userManager.CreateAsync(newUser, model.Password);

                    if (result.Succeeded)
                    {
                        await _signInManager.SignInAsync(newUser, false);
                        _logger.LogInformation($"New user account created: {model.Username}");

                        return RedirectToAction("Index", "App");
                    }

                    _logger.LogError($"Registration failed for {model.Username}: ", result.Errors);

                    return View(model);
                }

                return View(model);
            }
            catch (Exception ex)
            {
                _logger.LogError("Database Failure: ", ex);
                return View(model);
            }
        }

Estoy aprendiendo asp.net y estoy tropezando aquí con lo que espero que sea un error obvio, ya que parece ser un problema de conexión básico, pero no tiene sentido ya que la base de datos puede consultarse utilizando IdentityDBContext pero no a través del UserManager, que en mi entendimiento utiliza la conexión IdentityDBContext.