So you are seeing the alert window (for the variable value), but it is empty, or does it say 'undefined' or 'null'? Have you confirmed that these are exactly the names of the variables - case-sensitive and no trailing space or anything like that? Since this is onChange, you can use newValue for the request_access script variable, or in the if condition. It would be super weird if you alert on newValue and it is empty, after having selected a user in the reference field.
