Did you follow the instructions in https://www.trisul.org/docs/howto/installseco.html Section 3 ?
Trisul picks up the alert from a Unix socket that barnyard2 writes to. The unix socket is named
barnyard2_alert The location depends on your interface name. Can you check if you have a directory similar to the one shown below ?
You put that in the trisulConfig.xml file - it will look something like
Do the other parts of Trisul work like PCAPs, Statistics, Flows??