Health Check not replacing the instance

Question

Hello,

I am new to the Microsoft Azure and experimenting few things,

We have S3 Standard App service plan(Dedicated App Service plan). We have manual scaling of 1 instance( I know we need more instances for fault tolerance but for now assume we have 1 instance).

We have 9 Azure functions and 2 Webapps. None of the apps have health check enabled apart from 1 function.

We have configured health check endpoint and enabled health check on one function and this function becomes unhealthy after sometime and we can see the health status has unhealthy and since we have 1 instance, it actually needs to replace the instance after 1 hour of continuous unhealthy pings. I don't see the instance getting replaced. What may be the reason for this?? (I know max of 1 instance can be replaced and 3 in 1 day but nothing was replaced as this is the first time I am enabling the health check)

I tried enabling the auto heal rule(CollectAnalyseKill) which terminates the w3wp.exe process once the rule threshold is met and starts a new w3wp.exe(function). - This is like restart of a function is what I felt but it doesn't replace the whole instance(stopping all the functions and starting all the functions on a new instance)

What is the use of health check without auto heal enabled? Does this come into effect only if we have more than 1 instance in our App Service plan?

Microsoft portal says

"Your site has a single instance which will not be removed if it becomes unhealthy. However, after one hour of continuous unhealthy pings, the instance will be replaced. You can still set up Azure Monitor Alerts based on the health status."