Hi,
403 is a client side error. If you are able to see that 403 is sent by Application Gateway, that means your backend is responding with 403. To understand why it responds with this 403, I would like the following info from your end:
- Fiddler tracer when you access your site via Application Gateway
- Screenshots of your Application Gateway settings - Probe, HTTP Settings, Rule, Listener, Backend Health Status
This can help us understand how Application Gateway would be sending the request to your backend and we can figure out why your backend is responding with 403.
Regards,
Karthik Srinivas