The Webhook Secret (Root Planner tab, next to API Token) is a private password that Root Planner must include every time it sends a route update back to Sprwt. Sprwt rejects any incoming route update that does not carry the matching secret, so nobody else can inject routes into your account. It is generated automatically for your account, and Sprwt registers it with Root Planner together with your site address whenever it (or the API Token) is saved from the super-admin system Config page; you normally never need to touch it. If it is empty, Sprwt refuses all incoming updates ("Webhook Secret Not Configured") and the Sync Report stays empty.