user alert on apm logs

I try to trigger a command when a specific log is written on /var/log/apm

It works on 2 different non prod big-ip, but on a third one in production it only works with /var/log/ltm logs.

user_alert.conf

"failed" is commun in my ltm logs. "New session" is commun in apm logs.

So this works (triggered from ltm logs):

alert test "failed" { exec command="logger -p local0.notice 'test'" }

This doesn't (not triggered from apm logs):

alert test "New session" { exec command="logger -p local0.notice 'test'" }

Do you have any idea why?