Issue launching Firefox

Hi, I am having the attached problem when trying to execute a Script that Browses on Firefox.

Tks for the help!

The Script Code:

function TEST_FF()
{
var BrowserItems, i;

BrowserItems = new Array(1);
BrowserItems[0] = Browsers.Item("firefox");

stUsername = "user_example";

for(i = 0; i < BrowserItems.length; i++)
{
let url = eval("CustomUtils.getTestURL()");
BrowserItems[i].Run(url);
let page = Sys.Browser("*").Page("*");

// Campo obUsername
let obUsername = page.FindElement("//input[@name='username']");
if (!strictEqual(obUsername, null))
{
obUsername.Click();
obUsername.Keys(stUsername);
Log.Message("Input obUsername: " + stUsername);
Log.Picture(Sys.Desktop.ActiveWindow(), "Ingreso Username");
}
else
{
Log.Error("\"obUsername\" no se encontró.");
}
}
}