does anyone know what can trigger a custom gl plugin other than user interaction. I tried configured a scheduled script that will load and save a record but it doesn't run the plugin. User interface and CSV import works fine. Might be related to the -System- user

As far as I know, the custom gl plugin should trigger when you save the record regardless of the context. I have a done a custom GL plugin for Item Fulfillment. This gets triggered when another script creates the item fulfillment.

if it was a user event script I wonder if its because it carried the user profile.

It was a Suitelet, so you might be right