my ec2 instances immediately shut down

I would make sure you are using the below AWS Sandbox requirements:

EC2 Limits

Create EC2 instances in US-EAST-1 (N. Virginia) or US-WEST-2 (Oregon)

ONLY these Instance Types are allowed:

t2.micro to t2.medium

t3.micro to t3.medium

Max Volume Size of 50GB

Max Volume IOPS of 150

No Elastic GPU

For more on the AWS Sandbox, see:

https://help.acloud.guru/hc/en-us/articles/360001389256

In addition to the above limits, make sure your user role has access to the KMS key that encrypts the EC2’s EBS volumes, if any. Otherwise, you will get a client error.