I suspect you do not implement get_elem correctly. This callback needs to response to an invocation with a path like /alarms/alarm-inventory/alarm-type{X Y}/alarm-type-id (or generally, for any list the data provider needs to be able to handle get_elem targeted at the list’s first key element). ConfD uses this to verify whether given instance exists and your DP needs to respond with the key value if it does, or not_found if it does not.
Se developerLogLevel to trace and have a look at your devel.log, ConfD logs every callback request/response there.