If it's any help, the Ruby code posted the following parameters

AccessKeyId => <accessKeyId>
Action => SendSms
Format => JSON
PhoneNumbers => 7766
RegionId => default
SignName => iiuy
SignatureMethod => HMAC-SHA1
SignatureNonce => 7e44843695e9a68247e15d3beb018b63
SignatureVersion => 1.0
TemplateCode => jkk
Timestamp => 2019-09-02T16:28:32Z
Version => 2017-05-25
Signature => TquzjlguNxK2WdUVVrfm4yYTHZI=

code snippet from rpc_client.rb

def default_params
      default_params = {
        'Format'           => 'JSON',
        'SignatureMethod'  => 'HMAC-SHA1',
        'SignatureNonce'   => SecureRandom.hex(16),
        'SignatureVersion' => '1.0',
        'Timestamp'        => Time.now.utc.strftime('%Y-%m-%dT%H:%M:%S
+Z'),
        'AccessKeyId'      => self.access_key_id,
        'Version'          => self.api_version,
      }
      default_params.merge!('SecurityToken' => self.security_token) if
+ self.security_token
[download]

Also this looks wrong

$req->header('Content-Type' => 'application/json; charset=UTF-8');
[download]

The content-type in the header was

application/x-www-form-urlencoded

poj