Can't Launch EC2 Instance in Local Zone (Root EBS Volume Stuck in Attaching)

My EC2 Instance in the Las Vegas local zone is stuck in the pending state, and its root EBS volume is stuck in the attaching state.

I have an identical launch template for just the US-West-2 region (including encrypting the volume, which local zones require), and it works fine.

Any idea why a local zone would behave differently?