Geb script ruuning on IDE but not on Load UI 2.5.3

Hello all,

I am trying to make a web load test about registering users from a form and then login and verifying the correct user name match.
The users are generated dynamically and put on a csv file.

I'm using GebRunner with a 'Usage' generator.

Here's my script is :

Browser.drive {
   
        go "http://localhost:8090/myapp/register/"
         assert (title == 'Login')
        
        //Register
        $("form").with {
            userName = "UserLoadTest-786"
            password = "password"
            repeatPassword = "repeatPassword"
            firstName = "firstName"
            lastName = "lastName"
        }
        $('#submit').click()
        sleep(2000)
        assert $('.username').text() == "firstName lastName"

As mentioned before, it works perfectly well from my IDE...but from load ui, the users generated can't login because they have not being created.
And I have an assertion error:

assert $('.username').text() == "firstName lastName"
| | |
[] null false


Please could you provide some help with this issue?