S3 backend not working

Terraform
1

Hello,

I am trying to use S3 backend with IBM Spectrum Scale.

Reading different posts , I did this config

backend.tf

terraform {    
  backend "s3" {    
    region   = "any"    
    access_key = "my_key_id"    
    secret_key = "my_key_secret_id"    
    endpoint = "https://scales.xxx.local:8081"    
    max_retries = 1    
    force_path_style = true                          
    skip_requesting_account_id = true    
    skip_credentials_validation = true    
    skip_get_ec2_platforms = true    
    skip_metadata_api_check = true    
    skip_region_validation = true    
  }    
}

staging.tfbackend

key = "staging.tfstate"
bucket = "staging"

I run terraform init and I received this error :

2020/10/15 12:46:39 [DEBUG] [aws-sdk-go] <?xml version='1.0' encoding='UTF-8'?>
<Error><Code>SignatureDoesNotMatch</Code><Message>The request signature we calculated does not match the signature you provided. Check your key and signing method.</Message><RequestId>xxxx</RequestId></Error>
2020/10/15 12:46:39 [DEBUG] [aws-sdk-go] DEBUG: Validate Response s3/GetObject failed, attempt 0/1, error SignatureDoesNotMatch: The request signature we calculated does not match the signature you provided. Check your key and signing method.
	status code: 403, request id: xxxx, host id: yyy
Error refreshing state: SignatureDoesNotMatch: The request signature we calculated does not match the signature you provided. Check your key and signing method.
	status code: 403, request id: xxxx, host id: yyy

Any idea ? I tested the credentials with Cyberduck and it worked

Regards