When first setting up a Perforce triggered build or changing the polling configuration it can be hard to debug issues.
After a poll that found no changes there's nothing in the P4 Trigger Log to indicate when the webhook was last called. In that case there's no way to distinguish between the poll running again but not finding changes, or the poll not happening any more.
Adding the date and time to the P4 Polling Log would make it easy to confirm that the poll is running when expected.