The following error occurs when creating machine catalog after upgrading XenDesktop to 7.12:
XDDS:2367399e

1. Expand the Configuration node in the tree control on the left-hand side of the console.
2. Select the Hosting node
3. The hosting connections are listed in the middle pane. Select your AWS hosting connection and click on Edit Connection on the right.
4. Select the Advanced tab of the edit dialog when it appears.
5. In the Connection Options text box, add the parameter UseExplicitVpcForVolumeWorkerBootstrap=true. This will allow the use of AWS EC2 Classic Instance for the Volume Worker VM.

Problem Cause

XenDesktop 7.12 is using a new AWS instance type for volume worker VMs, and they have to run inside a VPC. The current account in AWS still supports EC2 classic.