Issue about connecting with AWS API

Dear,   when I use Call Rest to connection with AWS API. I get an Message: Forbidden. But in AWS I also can’t find this POST request. Following is the Microflow: Is there any wrong setting in my SigV4Builder or SigV4Parameter or Call Rest Header?  
1 answers

Maybe this is the reason. our host is located in But the host which is generated by Get SigV4 Headers is 
I also update this host in Rest Call, but this is useless. Because the Authorization is generated with, not