How to solve Error loading state: AccessDenied: Access Denied status code: 403 when trying to use s3 for terraform backend?

My simple terraform file is:

provider "aws" {
  region = "region"
  access_key = "key" 
  secret_key = "secret_key"
}

terraform {
  backend "s3" {
    # Replace this with your bucket name!
    bucket         = "great-name-terraform-state-2"
    key            = "global/s3/terraform.tfstate"
    region         = "eu-central-1"
    # Replace this with your DynamoDB table name!
    dynamodb_table = "great-name-locks-2"
    encrypt        = true
  }
}

resource "aws_s3_bucket" "terraform_state" {
  bucket = "great-name-terraform-state-2"
  # Enable versioning so we can see the full revision history of our
  # state files
  versioning {
    enabled = true
  }
  server_side_encryption_configuration {
    rule {
      apply_server_side_encryption_by_default {
        sse_algorithm = "AES256"
      }
    }
  }
}

resource "aws_dynamodb_table" "terraform_locks" {
  name         = "great-name-locks-2"
  billing_mode = "PAY_PER_REQUEST"
  hash_key     = "LockID"
  attribute {
    name = "LockID"
    type = "S"
    }
}

All I am trying to do is to replace my backend from local to be store at S3. I am doing the following:

1. terraform init ( when the terrafrom{} block is comment )

2. terrafrom apply - I can see in my AWS that the bucket was created and the Dynmpo table as well.

3. now I am un commenting the terrafrom block and again terraform init and i get the following error:

Error loading state:
    AccessDenied: Access Denied
        status code: 403, request id: xxx, host id: xxxx

My IAM has administer access I am using Terraform v0.12.24 as one can observe, I am directly writing my AWS key and secret in the file

What am i doing wrong?

I appreciate any help!

  backend "s3" {
    bucket = "great-name-terraform-state-2"
    key    = "global/s3/terraform.tfstate"
    region = "eu-central-1"
    access_key = "<access-key>"
    secret_key = "<secret-key>"
  }
}