UCCE 11.5 to the CVP I get 30,000 per day , number off call like 100 per day that fail .
in the CVP log I see calls that fail I see this error.
[INBOUND]: Refer failed with 404 - Not Found. May be a problem with Routing Configuration or Gateway Dial-Peer. [id:5004]
%CVP_11_5_SIP-3-SIP_CALL_ERROR: CALLGUID = 19951E751DAE11EABDA7A0E0AF4C6140 LEGID = 19959347-1DAE11EA-B112C1C8-69C88993 -[INBOUND] - ABNORMALLY ENDING - SIP code , Reason Hdr [Q.850;cause=38] Q850 Reason [38 - Network out of order, typically a TCL script abnormal disconnect.], GW call using SURV TCL flag [false], NON NORMAL flag [true], DNIS , ANI  with AGE (msecs) 132360 and Call History : 11111111117738|
how can I find the problem that the call fail .
all customer dial to the same number .
I would search the cvp log and error log with the CALLGUID of the failed call for more details.
Usually I faced such errors, when the Media Server address was incorrectly filled or was empty or when the media file to play was missing.
There are one of two issues occuring.
1) that CVP is removing all your endpoints - due to a network issue for a period of time so has nowhere to route the call to.
2) that when the call is routed to the end point the call fails
I think that option 2 is the most likely - but your CVP Error and call logs would confirm 100%.
If it is indeed option 2 - you then need to determine why that gateway fails to route the call.
What I would do is setup syslog on the gateway and enable sip and ISDN debugging.
e.g. debug ccsip messages, debug isdn q931
And make sure your syslog is set up to forward debug output to your syslog servers.
Since you don't know which gateway this fails on - you will need to do it on all your gateways / endpoints.
Then a call fails - match up the failed call with the syslog logs and see if you can detemine the root cause of the failure.