In ADFSWAP Servers, You will see that ADFSSVC and APPPROXYCTRL are running but APPPROXYSVC is in stopped state:
In Event Viewer, You will get the below event
The Above event is triggered when Trust relationship between ADFS and ADFS Proxy has broken.
Open PowerShell in the ADFS Proxy Server where you found APPPROXYSVC is not running and run the below command.
Install-WebApplicationProxy –CertificateThumbprint ‘1f83f462c3debd4d0820ae26ccca3708309ba101‘ -FederationServiceName ADFS.Windowstechpro.com
You can see that APPPROXYSVC is running and ADFS Configuration retrieved successfully.