EC2 can't retrieve the name because the AMI was either deleted or made private How to resolve

Once an EC2 instance is launched it has no dependency with the AMI from which it has been launched even if the AMI is de-registered. Even though the AMI gets registered there won't be any effect on the running instance. Below article confirms the same statement: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/deregister-ami.html

When an AMI gets deprecated it cannot be seen on AWS console. Although, we can view the those details from AWSCLI.

More details about deprecated(deregistered) AMI:

• The deprecated AMI does not appear in DescribeImages API calls unless you specify its ID or specify that deprecated AMIs must appear. AMI owners continue to see deprecated AMIs in DescribeImages API calls.
• The deprecated AMI is not available to select via the EC2 console. For example, a deprecated AMI does not appear in the AMI catalog in the launch instance wizard. AMI owners continue to see deprecated AMIs in the EC2 console.

In order to view the AMI details, describe-images command can be used. The following command will list the details such as name, image id, creation date, deprecation time, image owner alias.

$ aws ec2 describe-images --region <RegionID> --image-ids <AMIid>