My trigger type is ‘REST hook’. But still is showing warning from ‘Polling’. How can I solve this error?

The polling request is used, when the user is configuring your trigger in the Zap editor. It’s there to fetch objects they can use for field mapping when configuring subsequent Zap action steps.  Rest hooks otherwise have no data to work with.  The objects fetched need to match the hook payload in terms of content and data shape.  Zapier requires this request to be configured for all hook-using integrations in the app directory.