title: Shiny apps won't launch in RStudio
body: <p>I just installed R 4.1, RStudio 1.4, and the Shiny package. I'm trying to launch the most basic Shiny app using the green &quot;Run App&quot; button :</p>
  <pre><code>library(shiny)
  
  ui &lt;- fluidPage(
    'Hello world'
  )
  
  server &lt;- function(input, output, session) {
    
  }
  
  shinyApp(ui, server)
  </code></pre>
  <p>However, I get nothing. The console shows the final line, followed by a blank output line :</p>
  <pre><code>&gt; runApp('Projects/Shiny tutorial/main.r')
  
  </code></pre>
  <p>Plus the R session cannot be terminated.
  My default browser is Firefox, and I'm running Windows 10.
  Any idea what may be wrong ?</p>