In the October 2018 releases of the UC firmware, Polycom have removed the ability to reboot a phone using the checksyncreboot command. This still works with non-UC firmware, however we are now implementing the REST API reboot command as the main method of reboot although initially both methods will be work if the phone supports it. The two methods for enabling reboot from UDM Pro are:
Include the provided "Polycom_checksync_alwaysreboot_enabled" device profile in the All Devices tag.
For REST API reboot
You must change the admin password on the phones from the default. You can do this with the provided "Polycom_Security_AdminPassword" device profile as a template just edit this and change the password.
You will also need to create a new Device Profile and include the attribute "apps.restapi.enabled" with a value of Yes (1)
Both of these should then be included in the All Devices tag.