4452d530_able___FreeSWITCH___Confluence__Description
[ITU-T Q.850 Code] 1 [SIP Equiv.] 404 [Enumeration] UNALLOCATED_NUMBER [Cause] Unallocated (unassigned) number [Q.850 value 1] [Description] 
This cause indicates that the called party cannot be reached because, although the called party number is in a valid format, it is not currently allocated (assigned).
Hangup Cause Code Table - FreeSWITCH - Confluence
Description