Javascript code not injected Form-based

Hello,

I am trying to do a A/B Test, it has to be form-based. Our web page is build on SPA.  I login, then go to the specific page I want to see my code and the problem is that our code is not being injected there. I put the setInterval, I did the Audience Refinements in a right way but I don´t know what is happening

This is part of my code: 

<script>
var checkExist_alternativa = setInterval(function() {
//Si existe el elemento, cancelamos el interval y ejecutamos el código necesario
if (jQuery("#contract").length >= 1) {
clearInterval(checkExist_alternativa);

var nuevo = document.getElementById('contract); //SELECT THE ID WHERE I WANT TO INJECT MY NEW CODE
var htmlAB = ' HTML CODE';
nuevo.insertAdjacentHTML('afterbegin', htmlAB); //NEW HTML
var cssAB = '<style>CSS CODE</style>';
nuevo.insertAdjacentHTML('afterbegin', cssAB); //NEW CSS
}
}, 100);

</script>

Anyone knows how to solve this?

Thank you for helping me!