I have my ssm parameter store set up in one of the aws account (account Source). I want to access the parameters in another aws account (account target). Earlier parameter store did not directly allow to share parameter in cross account. I came across this article that says now paramter store can access parameters in cross account using Resource access manager

https://aws.amazon.com/about-aws/whats-new/2024/02/aws-systems-manager-parameter-store-cross-account-sharing/#:~:text=To%20share%20parameters%2C%20you%20add,see%20Working%20with%20shared%20parameters.

I have added my parameter in RAM in Source account and gave target account execution role permissions to access this parameter.
Now i need to fetch the parameters programatically.

def fetch_parameters(key):
    ssm_client = build_client(service="ssm", region=get_aws_region())
    result = ssm_client.get_parameters(Names=[ARN], WithDecryption=True))
    return result["Parameters"][0]["Value"]

I’m executing this code from Target account and getting the following error:
IndexError: list index out of range

Can someone please guide on what’s missing. Thanks!