4452d530_able___FreeSWITCH___Confluence__Description
[ITU-T Q.850 Code] 99 [Enumeration] IE_NONEXIST [Cause] Information element / parameter non-existent or not implemented [Q.850] [Description] 
This cause indicates that the equipment sending this cause has received a message which includes information element(s)/parameter(s) not recognized because the information element(s)/parameter name(s) are not defined or are defined but not implemented by the equipment sending the cause. This cause indicates that the information element(s)/parameter(s) were discarded. However, the information element is not required to be present in the message in order for the equipment sending the cause to process the message.
Hangup Cause Code Table - FreeSWITCH - Confluence
Description