While managing your instances in the current OpsWorks stack, you suddenly started getting the following error.

Answer options:

A.Check the IAM role which was attached to the instance.
B.Check if the EC2 instances were manually added to the ELB.C.Check if the stack is configured properly.
D.Check if the OpsWorks client is configured properly.

Answer: A and
B.This can occur if a resource outside AWS OpsWorks on which the instance depends was edited or deleted. The following are examples of resource changes that can break communications with an instance.
An IAM user or role associated with the instance has been deleted accidentally, outside of AWS OpsWorks Stacks. This causes a communication failure between the AWS OpsWorks agent that is installed on the instance and the AWS OpsWorks Stacks service. The IAM user that is associated with an instance is required throughout the life of the instance.
Editing volume or storage configurations while an instance is offline can make an instance unmanageable.
Adding EC2 instances to an ELB manually. AWS OpsWorks reconfigures an assigned Elastic Load Balancing load balancer when an instance enters or leaves the online state. AWS OpsWorks only considers instances it knows about to be valid members. Instances that are added outside of AWS OpsWorks, or by some other process, are removed. Every other instance is removed.
For more information on troubleshooting OpsWorks, please visit the link:
http://docs.aws.amazon.com/opsworks/latest/userguide/common-issues-troubleshoot.html