Problem whit Ajax in CI 3.1.10

Hello, I have an issue whit a select that get the options from ajax. When I click Submit button, it foes not send the value y selected via $_POST. I used the enable_profiler and it shows that only the name and the level where sended:

$_POST['name']
$_POST['level']

The third element, which is the ajax select, was not there.

Can you help me?

Thanks in advance.