The most recent release of Datomic resulted in an AWS Marketplace misconfiguration while adding support for t3 instances, preventing cycling of existing t2 instances.
We are working with AWS to rectify ASAP but if you encounter an autoscaling group that fails to launch new instances with the error:
Launching a new EC2 instance. Status Reason: The instance configuration for this AWS Marketplace product is not supported. Please see the AWS Marketplace site for more information about supported instance types, regions, and operating systems. Launching EC2 instance failed.
the current mitigation is to upgrade your stack to the latest release (482-8794).