What could be causing this problem?
(Choose two.)
The AWS account has reached EC2 limits for the Region.
The AWS account has reached EC2 limits for the Availability Zone.
An EC2 key pair has not been specified.
The EC2 instance is missing an instance profile with ec2:RunInstances permissions.
The subnet being used has no more usable private IP addresses.
Explanations:
Reaching EC2 limits for a Region would prevent new instances from launching. AWS imposes limits on resources per region, such as the number of instances.
EC2 limits are set at the Region level, not the Availability Zone level. Therefore, reaching limits in an AZ won’t prevent launching an instance.
While an EC2 key pair is required for SSH access, the instance itself can still launch without it. Lack of key pair only impacts login.
EC2 instances can launch without an instance profile, as long as no specific IAM permissions are required by the instance at launch.
If the subnet has no usable private IP addresses left, the EC2 instance cannot be assigned an IP and will fail to launch.
I sort that the answer is:
The AWS account has reached EC2 limits for the Region.