Unable to Deploy Windchill application hosted on Azure VM to Azure Application Gateway

Windchill application is hosted on Azure VM using VMs_FQDN:81. We are trying to deploy the application hosted on Azure VM to Azure Application Gateway. We want to expose application for external users so that they can access the application outside the VM.

Application URL -- http:/FQDN:81/Windchill/app

Configured APP_POOL(VM on which application is hosted), Listeners(Port 80,81), BACKEND_SETTINGS(for Port 80 & 81), Routing Rules(Path Based routing rule-- 

Heath probe is showing unhealthy.