@Uday Kasula Thanks for reaching out. I will suggest you to review the Diagnose and solve problems blade on your function app to get more insights why you are observing "Azure Functions runtime is unreachable" and the action plan to resolve issue. The issue could also be observed is there is a connecting issue with the storage account I will also suggest you to review Troubleshoot error: "Azure Functions Runtime is unreachable" document.
In case you are still not able to find the root cause of the issue then please refer to my private comment so I can assist you further.