How to deploy WES images via WMS?

Hi,
I don’t know why it seems to be so much more difficult deploying a certain image via WMS than it was with WDM.
In WDM I could just right-click a device, run the Package Distribution Wizard, select the appropriate image and: boom, Merlin did it’s thing. Done.

In WMS I cannot get this to work with WES images. According to the Administrators Guide I created a subgroup (DeployImage), created a WES image policy, assigned the group (DeployImage), set the OS type (WES), selected the OS image, set the deployment rule to “Force this version” and set the Apply Policy Automatically to “Do not apply automatically”.
After that, I added the device to be flashed to the group DeployImage and scheduled a job to deploy it immediately.

The WDA client on the device shows the correct group but nothing happens. The scheduled job in WMS shows the status “Completed” but no device was affected: Success: 0, Pending: 0, In-Progress: 0, Delayed: 0, Failed: 0, Canceled: 0.

I honestly don’t know what I’m doing wrong. Can anyone help?