Hello Anshuman Srivastava,
Welcome to the Microsoft Q&A and thank you for posting your questions here.
I understand that you're having issue with application gateway not able to route properly.
Among many things you can check are Listener Configuration, DNS Configuration and Routing Rules.
Most of all, v2 SKU can affect how requests are routed so, make sure that multi-site listeners are processed before basic listeners unless rule priority is defined - https://learn.microsoft.com/en-us/azure/application-gateway/configuration-listeners
Also, you can use tools like Azure Network Watcher to diagnose and troubleshoot network issues and if you have logs enable, review and let see more error or information that you get.
I hope this is helpful! Do not hesitate to let me know if you have any other questions.
Please don't forget to close up the thread here by upvoting and accept it as an answer if it is helpful.