Hi there, the problem is the webhook module you are using. A while back they created a bunch of monday webhook modules, and at that time the Webhook version stopped working (don’t know the details of why). So create a new webhook using one of the monday modules - they all start with “Watch.” I usually use the least specific one “Watch Events” (at the very bottom of the modules list) because then I can still pick my specific trigger in monday. On the monday side, you’ll still select the Webhooks app as usual and select your trigger integration. Then just paste in the webhook addy given to you in the monday “Watch Events” module.
Many of the other monday webhook “Watch” modules that are more specific will create the webhook on the monday side all on their own, you don’t have to set up the trigger integration.