Enable Always On when running on dedicated App Service Plan

Azure Functions can run on either a Consumption Plan or a dedicated App Service Plan. If you run in a dedicated mode, you need to turn on the Always On setting for your Function App to run properly. The Function runtime will go idle after a few minutes of inactivity, so only HTTP triggers will actually "wake up" your functions. This is similar to how WebJobs must have Always On enabled.

To turn on Always On, go to Function App Settings -> App Service Settings -> Application settings -> Always On. (Tip: you can also search for "Always on" in the search box at the top.)