Check out this bug. It might be your issue.
CSCsy58015 Bug Details
Http trigger does not work when failover occurs
Symptom:
http trigger, from where they are passing the parameters to the script. It works fine when the Node1 is mater... if it fail over to Node2 then the information is not passed to the script.
Conditions:
HA setup and if it failover to 2nd Node.
Workaround:
Make changes to asp/http file where they have the ip address of the Node1 to Node2
1st Found-In
5.0(1)SR1
7.0(1)SR1
Fixed-In
7.0(1.2.93)
Jim