Invalid_Credentails

Hi Team, 
I have used cloud formation template to set up role , so that i can connect with AWS acount with dynatrace, 

https://github.com/dynatrace-oss/cloud-snippets/blob/main/aws/role-based-access/role_based_access_no_AG_template.yml

But i am getting Invalid_Credentials , error message, i did all the steps as described in the document.