Use "block".

_layouts/index.html

@@ -23,7 +23,7 @@
             }).then(function () {
                 document.getElementById('version').innerText = 'v' + amber.globals.Smalltalk._version();
                 document.querySelector('.try button').disabled = false;
-                document.querySelector('p.try').style.display = "initial";
+                document.querySelector('p.try').style.display = "block";
             });
         });
     </script>