Passing a local variable as input parameter to pop up doesn't keep value

We have a combobox that has a Local Variable set as Variable. We then have a button set to a method navigate that goes to a pop up which takes as input paramater the value of the local variable.
When debugging, the local variable is correctly assigned the value of the identifier selected with the combo box. When the button is press to open the pop up, in the preparation of the pop up the value of the input paramater is 0. We have tried to hard code the value of the input parameter and this was correctly passed to the pop up.
What should we do to make this work?

Kind regards

Hi Chiara,

Try the following, when you change the value of the combobox, refresh the button. You can do this by implementing the OnChange method of the combobox and using an AjaxRefresh in that flow to update the button - the button must have a name for you to reference it in the AjaxRefresh.