Although it sounds super trivial, I read about someone having the same problem that solved it by indenting the lines properly in your eventBridge configuration like so:
events:
- eventBridge:
eventBus: arn:aws:events:us-west-2:xxxxx:event-bus/order_events_dev
pattern:
source:
- 'aws.ec2'
detail-type:
- 'EC2 Instance State-change Notification'