Data Migration Services - Cannot connect to target

I'm evaluating AWS Data Migration Services. I'm attempting to move data from an Azure SQL database to a SQL Server 2016 database sitting on AWS RDS. I've successfully created the source and was able to connect when I clicked the Run Test button. However, when I entered the Target database connection details information, I'm not able to connect when I click the Run Test button. The information and error message is below.

I am able to connect to this instance using SQL Server Management Studio, with the credentials I'm using in the screen shot.

For timeout concerns, security groups are usually the culprit. Can you verify if the security group of your Target RDS instance allows ingress from the security group that the DMS Replication Instance belongs to?

See the attached screenshot:

See this article for more information: https://docs.aws.amazon.com/dms/latest/userguide/CHAP_Security.Network.html