Despite it’s related to the Zero Trust, may I ask just in case if the gRPC feature is enabled at the bottom of the page under the Network tab at Cloudflare dashboard for your zone where you’re gonna be using gRPC?
You get this error in the Console of the Developer Tools (F12), or it’s returned via HTTP request as a result to you?
Are you trying to access your own infra by one of the Gateway policies you’ve crated (DNS, Network, HTTP or proxy PAC?) and you’re autenticated via WARP app, or?
I haven’t tested that yet. However, with Network policy you should be able to use it