Error is seen adding a device to Digi Device Cloud or Remote Manager: "Failed to add one or more devices"

Problem:  

If you're trying to add a device to a Device Cloud or Remote Manager server and it comes back with the message “Failed to add one or more devices:” (see below), it may mean that your Digi device is already part of the inventory of an existing account.

Device is already in your own account:
 
Device is already assigned to another account:
 

Solution:

If you do not see the device within your own Device Cloud or Remote Manager account, Digi Technical Support can help find your device to see if a duplicate exists.