Test multiple Availability Zones test case from https://docs.google.com/document/d/11MT2DQWmEzy3Swg97pZ58hSXTstWVWQlK7kw4ysOi3k/edit?tab=t.0
Try to deploy HCP in multiple AZs. Subnets need to match those AZs.
Check that in AWS web console(or aws cli) that EC2 instances for machine pools in are created in correct region and Availability Zone.