AutoMapper.AutoMapperMappingException: 'Error mapping types.'

When I am mapping using mapper  between the model the error is being showed AutoMapper.AutoMapperMappingException: 'Error mapping types.'

I have the following model

  public class Country
    {
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int Id { get; set; }
        [Required]
        [MaxLength(50, ErrorMessage = "Country must be up to 50 characters in length")]
        public string CountryName { get; set; }
       public  ICollection<Author> Authors { get; set; }
    }


 public class CountryDto
    {
        public int Id { get; set; }
        public string CountryName { get; set; }
        public  ICollection<AuthorDto> Authors { get; set; }
    }

public class Author
    {
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int Id { get; set; }

        [Required]
        [MaxLength(100, ErrorMessage ="First Name cannot be more than 100 characters")]
        public string FirstName { get; set; }

        [Required]
        [MaxLength(200, ErrorMessage = "Last Name cannot be more than 200 characters")]
        public string LastName { get; set; }
        public  Country Country { get; set; }
        [NotMapped]
        public  ICollection<BookAuthor> BookAuthors { get; set; }
    }

    public class AuthorDto
    {
        public int Id { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
    }

startup.cs
public void ConfigureServices(IServiceCollection services)
        {
            services.AddDbContext<BookStoreDbContext>(options =>
        options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));
            services.AddControllers();
            services.AddScoped<ICountryRepository, CountryRepository>();           
            services.AddAutoMapper(typeof(Mapping));
        }

API Controller
 public IActionResult GetCountries()
        {
            var objList = _countryRepository.GetCountries();
            var mappedEntities = _mapper.Map<CountryDto[]>(objList);

            

            if (!ModelState.IsValid)
                return BadRequest(ModelState);

           

            return Ok(mappedEntities);
        }

Repository class

 public Country[] GetCountries()
        {
           // return _db.Countries.Include(a=> a.Authors).OrderBy(c => c.CountryName).ToList();
            IQueryable<Country> query = _db.Countries
                                   .Include(a => a.Authors);

            

            return  query.ToArray();
        }

Mapping.cs

 public class Mapping : Profile
    {
        public Mapping()
        {
            CreateMap<Country, CountryDto>()
                .ReverseMap()
                 .ForMember(a => a.Authors, a => a.Ignore()); 
        }
    }

When I map   the error is coming is as follows

AutoMapper.AutoMapperMappingException: 'Error mapping types.'