Ever notice that it can take two invocations to a Cortana skill to get it to work on Azure?
This is because resources are unloaded if they are idle for 20 minutes. The first invocation; you need to wait for the resources (web app service) to load. You can change this in basic and standard service plans by changing the app service’s settings to “Always On”.
But if you are using a free tier, what do you do? Set up an availability test that pings your web server every 15 minutes via an Azure web job or Azure monitor.