Parameter store error in ECS

We want to call parameter store values through our code dotnet application.

We are seeing the below error in our ECS container logs. ParameterStoreHelper : Something went wrong ; The service returned an error with Error Code ParameterNotFound and HTTP Body: { "__type": "ParameterNotFound" }

We are using the below code for the functionality.

Dictionary<string, string> values = new();
AmazonSimpleSystemsManagementClient client = new AmazonSimpleSystemsManagementClient(Amazon.RegionEndpoint.USWest2);

var bucketName = client.GetParameterAsync(new GetParameterRequest { Name = "testbucketname", WithDecryption = true }).Result;
values.Add("TestBucketName", bucketName.Parameter.Value);

Could any one help us how we can resolve this issue and call parameter store values in our application

Thanks in advance, Anil Kumar V.