AWS MGN: Data replication stalled

The "Data replication stalled" error you're experiencing with AWS Application Migration Service (MGN) could be due to several factors, but it appears to be related to security group creation issues.

First, it's important to note that forcing a specific Security Group in the Replication template instead of using the default option may not always resolve the issue. The error "Failed to create security group" suggests that there might be underlying permission problems or network connectivity issues.

Even though you've added the 'AdministratorAccess' policy to your MGN user, the problem might persist due to other factors. Here are a few things you can check:

1. Ensure that your AWS account has the necessary permissions to create and manage security groups in the target VPC.

2. Verify that there are no Service Control Policies (SCPs) or other organizational policies restricting security group creation.

3. Check the CloudTrail logs for any specific errors related to security group creation. This can provide more detailed information about why the creation is failing.

4. Ensure that there's proper network connectivity between the source server, the replication server, and the AWS MGN endpoint. The error could be a symptom of broader network issues.

5. Verify that the replication agent on the source server is running correctly and can communicate with the AWS MGN service.

If the issue persists, you might want to try re-initializing the AWS MGN service. To do this:

1. Open the AWS Application Migration Service Console and navigate to the correct region you are migrating to.
2. In the left navigation pane, select "Settings".
3. Under "Replication template," click "Reinitialize service permissions" and then click "Confirm."

This process can help resolve issues related to IAM service roles and permissions. If you continue to experience problems after trying these steps, it would be advisable to contact AWS support for further assistance, as they can provide more specific guidance based on your account and configuration details.
Sources
Common replication errors - Application Migration Service
Other troubleshooting topics - Application Migration Service