Replication Instance Fails to Connect to DMS Migration Endpoint

I am trying to use the Database Migration Service to move data between an RDS instance and Redshift.

Everything is configured on the same private subnet and same security group.

My target endpoint is the redshift cluster whose auth is protected via AWS Secrets Manager. The private subnet is having an issue communicating with AWS Secrets Manager because it does not live within the private subnet.

I have created a VPC endpoint, assigned to the same security group and added an inbound traffic rule to my security group that says allow Https traffic from this security group.

I get an error when testing the connection between the target endpoint and the Replication Instance: "Test Endpoint failed: Application-Status: 1020912, Application-Message: Failed in prepare imp for Redshift Failed to fetch Secrets Manager secret contents, possible reasons are missing secret attribute key or value, Application-Detailed-Message: Failed to retrieve secret. Failed to fetch Secrets Manager secret Arn 'REDACTED' contents, possible reasons are missing secret attribute key or value"

The secret it is trying to access is teh one created by redshift itself, I copied the full ARN. The role of the target endpoint is configured to allow GetSecretValue policy for this secret ARN as well.