Enrolled mobile devices might not work as expected, if a user source is deleted and the same user source is re-configured.
If a configured user source is deleted and the same user source is configured again, then you will be unable to manage mobile devices enrolled using the earlier user source.
Re-enroll the devices. As a best practice, ensure that you delete the device objects of these devices that are already present in ZCC and then re-enroll these devices.
Activation lock bypass code cannot be retrieved from an iOS supervised device
ZENworks 2017 Update 2
For some iOS supervised devices even if the Activation lock bypass setting is enabled in ZCC, the activation lock bypass code cannot be retrieved from the device.
Reset and re-enroll the device.