Running shiny documents in Rstudio Server



I am setting up an Rstudio server and everything is going really well. I have run into a problem with running shiny applications though. When I run the default Old Faithful Shiny app, the apps is rendered greyed out with just the number of bins slider bar showing. Also, when I run the following Rmarkdown document, the viewer pane shows please wait and does not stop. I can render Rmarkdown files just fine, but nothing with runtime:shiny in the YAML header.

title: "Shiny Document"
output: html_document
runtime: shiny

```{r, echo=FALSE}
numericInput("rows", "How many cars?", 5)

  head(cars, input$rows)


Anything in the shiny error logs?